It's the second-longest winning streak in NBA history, surpassing the 22 straight that Houston won in 2007-08 and trailing only the 33 in a row won by the 1971-72 Los Angeles Lakers.
James scored 37 with 12 assists as the Heat won in Boston in the regular season for the first time in 11 tries despite a career-high 43 points from Jeff Green. The Celtics were without Kevin Garnett, who has the flu and a left thigh strain.
Paul Pierce had 17 points, eight rebounds and eight assists for the Celtics. But he missed a 3-pointer with 3 seconds left that could have given Boston the win.