Last month, Trump said when asked about the allegations against Moore: "He denies it. Look, he denies it..."
While Trump has previously indicated his preference for a Republican to win the seat, this is his most explicit endorsement by name of Moore.
His comments on the Alabama Senate race Monday come after Trump tweeted saying the Republicans need Moore's vote in order to pass "massive Tax Cuts".
And President Trump tweeted of Moore on Monday: "We need his vote on stopping crime, illegal immigration, Border Wall, Military, Pro Life, V.A., Judges 2nd Amendment and more".
President Trump also had assailed Moore's Democratic rival Doug Jones, tweeting that "Putting a Pelosi/Schumer Liberal Puppet Jones into office in Alabama would hurt our great Republican Agenda of low on taxes, tough on crime, strong on military and borders.& so much more". If Jones defeats Moore next week, Republicans' Senate majority would narrow to just 51-49. "No to Jones, a Pelosi/Schumer Puppet!"
Trump will hold a rally on Friday in Pensacola, Florida, his campaign committee said last week - just miles from Alabama and four days before that state holds a controversial special election for a U.S. Senate seat.
"I endorsed Luther Strange in the Alabama Primary", the president added. That's despite an initial White House statement calling on Moore to step aside from the race, "if these allegations are true".
Multiple women have accused Mr Moore of inappropriate sexual conduct decades ago, when they were as young as 14. He says it didn't happen.
Trump himself has been accused of misconduct by several women, ranging from groping to unwanted advances and kissing, though these did not prevent his election previous year. The October 2016 release of an "Access Hollywood" tape revealed that Trump bragged in 2005 that he could grope and forcibly kiss women without their consent.
Before Thanksgiving, Trump did not rule out campaigning for Moore like he did for odd during the Alabama primary.
Trump briefly floated the possibility to reporters that he might campaign with Moore in Alabama, but the White House later clarified that Trump would not make any campaign appearances in the state.