Harden was greeted straight off his private flight with welcoming arms from Sixers' Daryl Morey.
Morey is also the one who tweeted out the video.
Harden headed to the team's facility to take a physical and is expected to be introduced on Tuesday.
Harden, who is averaging 22.5 points, 10.2 assists, and 8.0 rebounds per game this season, has missed the past week with hamstring tightness.
That issue saw him sit out his final three games with the Brooklyn Nets before Thursday's deadline-day blockbuster sent him and veteran big man Paul Millsap to Philadelphia in exchange for Ben Simmons, Seth Curry, Andre Drummond, and a pair of first-round picks.
Harden will eventually share a backcourt with Tyrese Maxey, who said it was surreal that someone he grew up watching is now going to be his teammate.
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ESPN contributed to this article.