American Vonn rested for three weeks, missing six races, because of an intestinal illness. She began training again a week ago.
She looked quick but slowed down the bottom section of the bumpy course to finish 24th, with Lara Gut leading the run.
"I'm really excited to be back, feeling good, feeling happy and strong," said Vonn.
"It's important for me because after being sick my legs just weren't strong anymore. At some point, you have to listen to your body."
Vonn was hospitalised for two days in November before winning three speed races at Lake Louise and the Super-G at St. Moritz.
She then crashed in the Val d'Isere downhill and failed to finish the opening run of the Courchevel giant slalom.
"Hopefully, we'll get a training tomorrow and I get comfortable on this course," Vonn said. "I think everybody feels tired at the end of this course, but I feel strong again and everything is good."
There will be a downhill and a Super-G this weekend.
Maria Hoefl-Riesch, who pipped Vonn for the overall title in 2011, said the course is a difficult one for her.
"This is not an easy race for Lindsey getting back to the World Cup," the German, who placed fifth in the training run, said. "It's bumpy from top to bottom.
"There is no section where you can really charge. This is a difficult course, even for Lindsey."
Swiss Gut led the field by more than a second, setting a time of a minute 8.31 seconds.
Second was Anna Fenninger of Austria with Italian Daniela Merighetti and Austria's Andrea Fischbacher just 0.01s further back sharing third.
However Gut was one of several skiers to miss a gate.
FRIDAY'S TRAINING WAS CANCELLED DUE TO HEAVY SNOW
1 GUT Lara SUI 1:38.31
2 FENNINGER Anna AUT 1:39.33
3 MERIGHETTI Daniela ITA 1:39.34
3 FISCHBACHER Andrea AUT 1:39.34
5 HOEFL-RIESCH Maria GER 1:39.43
6 SCHMIDHOFER Nicole AUT 1:39.58
6 GISIN Dominique SUI 1:39.58
8 MARCHAND-ARVIER Marie FRA 1:39.59
9 FANCHINI Nadia ITA 1:39.65
10 ROLLAND Marion FRA 1:39.66