Both players, acquired before Thursday's non-waiver trade deadline, debuted with the Mariners for the opener of three-game series, with Jackson batting leadoff and playing centerfield and Denorfia batting sixth and playing right.
Together, they help balance a lineup that had been short on right-handed options.
''Obviously you can see it gives us a lot more balance against left-handed pitchers with those guys in the lineup,'' Seattle manager Lloyd McClendon said. ''It gives us more options, and it also gives us more options off the bench.''
The Mariners acquired Jackson (.273, 25 doubles, 33 RBIs) in a three-way deal that saw them trade infielder Nick Franklin to Tampa Bay, with Rays ace pitcher David Price going to Detroit. Seattle acquired Denorfia (.242) from the Padres for minor leaguers Abraham Almonte and Stephen Kohlscheen.
Jackson, who is scheduled to become a free agent in 2016, said he's looking forward to a fresh start, as well as a reunion with McClendon, his former hitting coach in Detroit.
''You get to start fresh,'' Jackson said. ''You get to help a ballclub that is trying to advance, and I like that challenge. I've always been somebody that's up for a good challenge, and I see this as one of those.''
For Denorfia, going from a sub-.500 team to a postseason contender was a welcome change.
''I'm going on a couple hours of sleep and I feel like I had about a pot of coffee just walking in here,'' Denorfia said. ''I'm really looking forward to getting off to a good start
To make room on the 25-man roster, Seattle optioned rookie outfielders Stefen Romero and James Jones to Triple-A Tacoma.