The season marked the debut of a new universal aerokit, replacing the manufacturer-designed kits used from 2015–2017.
It was the final season for Verizon Communications as the series sponsor as well as being the final season that the series was broadcast by both ABC and NBC Sports. A new series sponsor will be introduced and NBC will be the sole broadcaster for the series beginning in the 2019 season.
Honda won the engine manufacturer's championship for the first time since 2011. Robert Wickens won Rookie of the Year despite missing the final three races after a crash at the ABC Supply 500 at Pocono. Will Power won the 102nd Indianapolis 500. Scott Dixon won his fifth IndyCar title, and is now second to A.J. Foyt's all-time record for United States open wheel titles. Dixon won three races over the course of the season.
On October 20, 2017, Verizon Communications announced that it would exit its title sponsorship deal for the series after the 2018 season. This will not affect its vehicle sponsorship with Team Penske.
PFC became the IndyCar Series' brake caliper supplier beginning in the 2018 season.
Kyle Novak was confirmed as Race Director on January 5, replacing Brian Barnhart, who left to become president of Harding Racing. The three-man stewarding panel of Dan Davis, Arie Luyendyk and Max Papis, introduced when Barnhart was first named Race Director, will remain intact.
On March 21, 2018, NBC Sports (which serves as the existing cable rightsholder of the series through NBCSN) announced that it would become the sole television rightsholder of the IndyCar Series from 2019 through 2021, replacing the previous split between ABC and NBCSN. Eight races per-season will air on NBC, including the Indianapolis 500.
All IndyCar Series machines will feature an all-new universal bodywork, inspired by CART's 1990s and 2000s bodywork, but still keep the Dallara DW12 chassis base. This new chassis configuration is dubbed the IR18, and will be used until at least 2022. For the first time since the 1996 Indy Racing League and 2007 Champ Car seasons respectively, cars will have a roll hoop without an airbox.
All IndyCar Series entrants will begin utilizing F1-style LCD steering wheel display dashes, a new Cosworth CCW Mk2 steering wheel with a configurable display unit, and new electronic components. The current Cosworth-Pi Research Sigma Wheel Display dash had been used since the 2000 season will be retired permanently, but several teams will opt to keep the old Cosworth Sigma Wheel Display dash for one more season due to cost reasons.
Due to the reduced amount of downforce produced by the 2018 spec aerokits, Firestone introduced new rain tires to improve grip in wet conditions for road/street races.
In the next step to increase driver safety through cockpit protection, IndyCar announced that Scott Dixon would test a windscreen, a possible alternative to the 'halo' device used by Formula One, at ISM Raceway on February 8.
The following teams and drivers are confirmed to compete in the 2018 IndyCar Series season. All teams use a specDallara IR18 chassis and Firestone tires.
Harding Racing confirmed a full-time schedule with Gabby Chaves after running part-time in 2017.Brian Barnhart was named President of the team on November 29, leaving his post as President of Race Operations and Race Director of IndyCar. Following the Road America round, Barnhart confirmed rumours that they wish to expand to fielding two cars as early as the latter part of the 2018 season, specifically naming Sonoma. He further confirmed the team was in talks with several drivers including current Indy Lights drivers.
After six seasons in the German Deutsche Tourenwagen Masters, Robert Wickens will make the switch to IndyCar to drive the No. 6 car for Schmidt Peterson Motorsports, replacing Mikhail Aleshin. Wickens previously replaced Aleshin in the first practice session at Road America in 2017, but did not get to compete in the race. Wickens suffered severe injuries in a crash at the 2018 ABC Supply 500 and was forced to miss the rest of the season. Due to damage incurred in the crash, the #6 car was withdrawn for the next race at Gateway. On August 29, SPM announced Carlos Muñoz as Wickens' replacement in the #6 car at the Portland and Sonoma rounds. 
On March 1, 2018 it was confirmed that Nazareth, Pennsylvania native Sage Karam would be returning to race in the 102nd Indianapolis 500 for Dreyer & Reinbold Racing. This will be the 3rd straight and 4th total Indianapolis 500 between them. The primary sponsor for Karam’s car will be WIX Filters.
On March 6, 2018 it was announced Conor Daly would be driving in the 102nd Indianapolis 500. He would be racing for Thom Burns Racing with Air Force as the primary sponsor.
On March 20, 2018 it was announced Pippa Mann would drive a 4th car for Dale Coyne Racing at the Indianapolis 500, with sponsorship from Donate Life Indiana.
On July 10, Harding Racing announced that Conor Daly would replace Gabby Chaves for round 12 in Toronto. The team also stated that they would experiment with their driver lineup for the remainder of the season in preparation for 2019. They want to test current top three Indy Lights drivers Colton Herta, Santiago Urrutia and Patricio O'Ward, the latter having already received a seat fitting with the team. Nevertheless Chaves is expected to return to the track in 2018 and remain under contract as the team's driver through 2019. Daly would be confirmed for the Mid-Ohio round on July 24.  On September 2, it was announced that 2018 Indy Lights champion Patricio O'Ward and 2018 Indy Lights runner-up Colton Herta would make their IndyCar debuts with Harding at the final round at Sonoma.
All manufacturer points (including qualifying points, race finish points, and race win bonus points) can only be earned by full-season entrants.
The top two finishing entrants from each manufacturer in each race score championship points for their respective manufacturer. The manufacturer that wins each race will be awarded five (5) additional points, which can be determined through bold in-line notation.
At all races except the Indy 500, the manufacturer who qualifies on pole earns one (1) point. At the Indy 500, the fastest Saturday qualifier earns one (1) point, while the pole position winner on Sunday earns two (2) points. It can be determined through italic in-line notation. But, in Gateway, as qualifying was rained out, no point will be awarded for pole position.
The manufacturer with the most points from each race is noted by an asterisk (*).
For every full-season engine used during the Indy 500 that reaches 2,000 total miles run, the manufacturer earns bonus points equal to that engine's finishing position in the race.
Ties are broken by number of wins, followed by number of 2nds, 3rds, etc.
^The qualification format for this race featured two separate qualification groups, with the fastest qualifier in each group earning a championship point; the faster of the two group fastest qualifiers would then start on pole, while the other would start from the outside of the front row. Andretti set the fastest overall lap, and was awarded the pole position. Scott Dixon set the fastest lap in the other qualifying group, and was also awarded a championship point.
^The qualification format for this race featured two separate qualification groups, with the fastest qualifier in each group earning a championship point; the faster of the two group fastest qualifiers would then start on pole, while the other would start from the outside of the front row. Rossi set the fastest overall lap, and was awarded the pole position. Robert Wickens set the fastest lap in the other qualifying group, and was also awarded a championship point.
^Qualifying for the Bommarito Automotive Group 500 was cancelled due to weather. The grid was set by entrant points, so Scott Dixon was gifted the pole position. Because of this, he was not awarded the bonus point typically awarded for qualifying on pole position.