While accepting the honour, he kept his speech short, but made sure to heap praise on the man who co-created Iron Man/Tony Stark, among other classic Marvel superheroes, reports dailymail.co.uk.
"Well look, I just got to come up here and open the show so I'll just say thank you Disney, thank you Marvel, thank you Russo brothers," the actor said.
"And most of all, to the late, great Stan Lee, this is for you, buddy," added the actor, who bid adieu to his superhero avatar with "Avengers: Endgame" this year.
The award ceremony took on Sunday in Santa Monica here.
Lee passed away in Los Angeles last November at the age of 95.
Following the news of his death, Downey Jr took to Instagram to pay tribute to the comic book legend, who co-created some of the most legendary superheroes that have entertained fans since Marvel was launched in 1961.
"I owe it all to you... Rest In Peace Stan... #MCU #Excelsior #legend #rip #StanLee #TeamStark," he wrote in the caption of a photograph of the Iron Man actor standing arm-in arm with Lee.
Showing his love and respect for Lee, Downey Jr. added a big red heart right in the middle of the photograph.
( With inputs from IANS )