In the 1983 season, Unser joined Team Penske and drove for 4 years in a Penske-owned car. Unser controlled the late stages of the 1983 Indianapolis 500, leading 61 laps. With less than 20 laps to go, Unser got challenges from Tom Sneva who led the most laps. With help from his son - who was several laps down - Unser began pulling away from Sneva. However Sneva got by Al Jr., and set sail for Unser Sr.. Sneva caught up to Unser within 1 lap of passing Al Jr., and passed him to retake the lead with 9 laps to go. Sneva then easily pulled away to win the race by 11 seconds, avenging his firing from the team in 1978. After the race, Unser Jr. was penalized 2 laps for his actions as well as having passed 2 cars under caution on lap 170.