The 17-year-old playmaker has penned terms until 2025 having made his competitive first-team bow earlier this month.
Maher, who initially joined the Saddlers aged 11, caught the eye over pre-season and has also made substitute appearances against Barrow and Swindon in recent weeks.
"I’m really happy and thankful to the head coach for giving me an opportunity and it’s time for me to kick on,” said Maher.
“My targets are to try and help the club progress, give the fans something exciting to watch and to cement my place in the squad.
“My family have been with me through thick and thin and they drive me on. They’ve said many times to keep my feet on the ground and stay humble – it’s probably the best thing you can do so I’m going to try and stick by that.”
Maher played in a friendly against Crystal Palace in the summer of 2021 before ending up as the top scorer for Walsall's under-18s last season.
The attack-minded midfielder properly established himself in the first team this summer and has recently trained with Ireland Under-19s.
Saddlers boss Michael Flynn added: "The hard work starts now for him.
“He’s a smashing kid, I’ve got a lot of time for him, nothing fazes him and he takes it all in his stride. He’s confident but not arrogant and he’s got ability.
“He’s got to keep grounded, level headed and work even harder than he has been and I’m sure he will.”