O.J. Mayo added 13 points and Marreese Speights had 12 to help the Grizzlies (19-15) move a season high-tying four games above .500. Gasol, who's headed to this weekend's All-Star Game in Orlando, finished three assists shy of a triple double.
Jrue Holiday scored 22 points - none in the fourth - for the Atlantic Division-leading Sixers, who shot just 37 percent while losing their fourth straight and sixth in their last eight. Rookie Lavoy Allen had 14 points for Philadelphia, and Andre Iguodala added 11 on 5-of-14 shooting.
Philadelphia trailed by 20 after the first period before rallying to pull within three late in the second and was down 47-42 at halftime.
Holiday scoring nine of Philadelphia's first 13 points of the third quarter to keep the Sixers close. His 3-pointer with 3:30 left made it 61-55.
Reserve guard Louis Williams hit another 3-pointer with 46.2 left in the third to pull Philadelphia to 64-60, but Memphis pushed its lead back to nine on back-to-back buckets by reserves Quincy Pondexter and Hamed Haddadi.
The Grizzlies allowed Philadelphia to get no closer than four points in the fourth. Tony Allen made a pair of key defensive plays down the stretch for the Grizzlies, forcing an airball by Iguodala with Memphis leading by five and later getting a steal on a Sixers fast break.
Gay then put the game out of reach with a 3-pointer with 2:10 left, helping Memphis improve to 6-3 this season on the second game of back-to-backs. The Grizzlies had fallen 97-93 on the road to Houston on Monday.
Playing a Sixers team that came into the game ranked first in the NBA in scoring defense, Memphis made seven of its first nine shots in building a 15-7 first-quarter lead. A Philadelphia timeout didn't slow the Grizzlies, who scored the next 12 points - including two 3-pointers by Mayo - to take a 27-7 lead.
Gasol was at the center of the run, getting four points, five assists and four rebounds in the first quarter.
Philadelphia trailed 30-10 after the first after shooting 4 of 20 from the field in the period. The 76ers' 10 points were the fewest Memphis has allowed in any quarter this season.
The Sixers finally got into an offensive rhythm in the second quarter, outscoring Memphis 9-2 over the first 3 minutes.
Holiday then made his first of three 3-pointers in the period with 5:13 left to cut Philadelphia's deficity to 10. He scored 13 straight points for the 7ters to pull them to 43-40 late in the quarter.
After an abysmal first quarter, the Sixers connected on 13 of their first 17 shots in the second and trailed by five at halftime.
NOTES: 76ers F Elton Brand (right thumb sprain) was a game-time scratch. ... Former world champion boxer James "Lights Out" Toney was among the 14,258 in attendance. ... At halftime, Memphis' mascot, Grizz, was introduced to the crowd as the team's second All-Star. Memphis' mascot has been selected to join Gasol at this weekend's All-Star festivities in Orlando.