England's Massaro, 32, trailed in the decisive fifth game but rallied to seal an 11-8, 12-14, 11-9, 8-11, 11-9 win.
The world number three also won the US Open on 18 October.
"It's amazing to win another major trophy - I'm over the moon," said Massaro. "Physically and mentally I feel in a really good place."
Egyptian world number one Mohamed Elshorbagy, 24, took the men's title, beating Frenchman Gregory Gaultier 11-5, 11-7, 5-11, 12-10 at the Khalifa Tennis and Squash Complex in Doha.
But it was Massaro's match - 73 minutes in length - which proved the most intriguing encounter as she came from a game down to eventually overcome El Sherbini, who is ranked five places lower.
"There's a lot of great names on that trophy so it's a great feeling to know that my name will go alongside them now," added Massaro, who closes the gap to Egypt's world number one Raneem El Welily and number two Nicol David, of Malaysia, with the win.
Great-Yarmouth-born Massaro also won the Macau Open in September.
Laura Massaro won a second successive PSA World Series title with a thrilling victory over Egypt's Nour El Sherbini at the Qatar Classic.