Left-back Lewis, 16, made his senior debut in our Betfred Cup Group H tie against Albion Rovers back on Saturday 16 July and has made a total of three starts already this term.
Eighteen-year-old wideman Tiffoney, meanwhile, marked his top-team bow by scoring a double in a friendly away at Livingston on 5 July and has gone on to make three starts and six substitute appearances in all competitions.
The pair’s present development squad deals were set to expire at the end of the current campaign but manager Jim Duffy was keen to reward the duo for their impact on the first-team.
He told gmfc.net: “Lewis and Tiff have signed their first professional contracts. Those new deals will take them up to the summer of 2018 and we’re absolutely thrilled the two boys have committed their future to the club.
“Part of your job as a manager is to try and develop young players for the first-team, and I think when the likes of Strappy, Tiff and Jai [Quitongo] get first-team opportunities it sends a positive message to the rest of the young boys.
“If they keep progressing and doing well and a chance comes their way then they’ll get the opportunity. That’s something that’s always important for clubs like Morton, to try and develop homegrown players.
“That takes a bit of time and patience, and there’s a lot of hard work put in by a lot of people in the youth system. The likes of Warren Hawke and Derek Anderson do the hard work and then we give the players the chance in the first-team.
“We only do that if we think they’re good enough and have the potential to be in and around the first-team, and for those boys to make their first-team debuts at 16 and 17 shows that we believe they are good enough to have a bright future in the game.
“Strappy and Tiff have shown already they can be a really positive addition to the first-team squad. We feel the boys have done well and deserved the offer of new contracts.”