The Revenant star, who took home the Best Actor statuette, brought Irmelin as his date for the big night at Los Angeles' Dolby Theatre.
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And, at the Vanity Fair Oscars afterparty, proud Irmelin was seen clutching tight to DiCaprio's new Oscar and smiled while the actor looked on.
DiCaprio usually brings his father George and Irmelin as his dates to awards shows. George was on hand for his son's 2016 Golden Globes best actor in a motion picture, drama, win in January.
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The 41-year-old spoke sweetly of his parents while accepting the Actors Inspiration Award at the SAG Foundation 30th anniversary party last fall, saying, "Irmelin, George – I would not be receiving this award and I would not be the actor that I am or be able to do any of the philanthropy that this job has given me the opportunity to have, and I wouldn't the person I am without the both of you, so thank you."
Sharing a similar sentiment in the Oscar press room on Sunday, DiCaprio said, "to have had parents that have allowed me to be a part of this industry, to take me on auditions every day after school and to tell stories like this has been my dream ever since I was four years old."
The 88th annual Oscars, hosted by Chris Rock, are being presented live on ABC from the Dolby Theatre in Hollywood, California.