The unusual gesture appeared in an Instagram video posted by the White House on social media. Obama is also wearing sunglasses as he arrived, with the first lady not far behind.
The video drew ridicule from some Instagram users, who saw the unorthodox salute as "un-presidential."
"Hopefully it was just a slip by this President," one user posted.
Others saw unnecessary nitpicking in the criticism.
"People are dying from disease, abuse or even hunger," another user commented on the video. "Priorities."
While it is protocol for U.S. service members in uniform to salute the commander in chief, it's not required for a civilian president to salute back, military experts say. Ronald Reagan is thought to have set precedent for the practice back in 1981.
However one feels about the latte salute, it's unlikely any coffee was at play. President Obama prefers hot tea.