The 20-year-old was called up to the Tykes' four-day championship clash with Durham at The Riverside.
Lyth, of Starbeck Close, in Whitby, opened Yorkshire's first innings on Thursday with a score of seven from 12 deliveries.
Durham had closed their first innings on 406 but the Tykes were put in a pickle by Graham Onions who took five wickets as Yorkshire slumped to 194 all out.
Lyth had taken a catch early Thursday morning to get rid of Onions after Michael di Venuto hit 184 for Durham.
Lyth won his place in the first team by virtue of some outstanding performances in the second XI this season.
And with Michael Vaughan on test duty for England against New Zealand, it has given Lyth the chance to shine - which he already has.
He smacked 127 in last week's triumph over Nottinghamshire at Stamford Bridge, his second century in three championship innings, having also struck 137 at Leicestershire.
Lyth has played several one-day games for Yorkshire, featuring in Friends Provident clashes and was part of the Tykes' squad which travelled to the United Arab Emirates to take part in a pre-season tournament.
A former England under 19, Lyth is considered by Yorkshire to be an outstanding prospect with a possible full England future ahead of him.
Speaking to the Gazette after day one of the Durham match on Wednesday night, Lyth said he was delighted to have been included.
"I kind of expected it as I've been doing well in the seconds and with Michael Vaughan on England duty, it's given me a chance," he said.
"Michael will be out almost all summer so I hope to get a few runs and cement my place in the side."
The game ends on Saturday.