Lohan said the nation should now get behind the President, despite his sexist comments about her in 2004 when she was a teenager.
“Look, I think always in the public eye you’re going to be scrutinised, and he is the President, so you have to – you have to join him. If you can’t beat him, join him," she said during a Facebook live interview with The Daily Mail.
The actress, who rose to fame in films such as The Parent Trap and Mean Girls before her well-publicised problems with substance abuse, spoke of her growing interest in Islam.
She called the religion “beautiful”, and did not rule out converting to Islam, saying: “Anything’s possible.”
She said she had been studying the Koran and that she was worried about returning to the US because of the current political climate and the executive order Mr Trump signed prohibiting citizens of seven Muslim-majority countries from entering.
“I was scared to come here with everything going on because of my personal beliefs,” she said.
Ms Lohan has recently spent time visiting Syrian refugee camps in Turkey, and urged Mr Trump to offer support to displaced people, in spite of his apparent determination to re-enforce his temporarily stayed travel ban.
The activist, who recently met with Turkish President Tayyip Erdogan, said: “Turkey really is doing a lot, and that's why I want to try and get the word out to Donald Trump to bring him over there, and have him see all the positive things that they're doing and how America can help as well.
“And I think it would be a positive thing for America to show their care and support, and for him to experience what it’s like for these people and experience how giving Turkey has been to the refugees.”
When asked who she would like to bring together to discuss the refugee crisis, she suggested some unlikely bedfellows, including her Mean Girls co-star Rachel McAdams.
“Angelina Jolie … Donald Trump…Putin – the more strong figures we have (the better)," she said.
“Brad Pitt …maybe someone like Rachel McAdams – the more the merrier in that situation.”
In January, following Mr Trump’s inauguration, Lohan took the high road when she had Mr Trump’s 2004 comments played back to her.
“I wish him all the best," she said.
"We live in a world of societies that consistently find fault in people. I think it’s a really scary factor. Taking someone else down is never the answer, and I think we all know that.”
Mr Trump said of the then-18-year-old Lohan in the 2004 radio interview with shock jock Howard Stern: “She’s probably deeply troubled and therefore great in bed.
“How come the deeply troubled women, you know, deeply, deeply troubled, they're always the best: in bed?”