The top-seeded Tsonga notched a 6-4, 6-4 victory over Ukrainian Alexandr Dolgopolov after the fourth-seeded Ljubicic outgunned Luxembourg's Gilles Muller, 7-6 (7-3), 7-6 (7-5).
Muller and Ljubicic engaged in a battle of serves to open Saturday's action, as neither broke serve throughout. Ljubicic dominated the first tiebreak, then raced out to a 4-2 lead in the second before letting Muller back into the match. Muller, after battling back to 5-5, lost the next two points to drop it.
Tsonga, meanwhile, broke serve three times and finished off Dolgopolov in 76 minutes. It was the Frenchman's first win over the Ukrainian in three meetings this year. Dolgopolov had beaten Tsonga in the third round at the Australian Open and again in the second round in Miami.
Sunday's final will be the third this year for Tsonga, who lost to Robin Soderling in the Rotterdam title match back in February and fell to Andy Murray at the Queen's Club before Wimbledon. The 10th-ranked Frenchman is 5-3 all-time in finals, but hasn't won a tournament since October 2009 in Tokyo.
Ljubicic, who won the Metz crown back in 2005, will play in his 24th ATP final and will try for his 11th title. His last came in April 2010 with a surprising run through the Indian Wells event that gave the 32-year-old veteran his first Masters triumph.
Tsonga and Ljubicic will meet for the third time in 2011. Tsonga prevailed in the Rotterdam semifinals before Ljubicic returned the favor in the second round at Monte Carlo to improve to 3-2 in the all-time series.
The 2011 Moselle Open titlist will collect $100,000.