The 35-year-old American trailed his Austrian counterpart by 0.4 seconds after day one in Sochi, but recorded a 106.3 to the Olympic bronze medallist's 113.5 on the jump to finish top of the pile with 19:39.7.
Tomaz Harp took third place, some 47.3 seconds behind his compatriot Gruber in second, with Japanese duo Akito Watabe and Yusuke Minato rounding out the top five.
Cristoph Bieler of Austria and Johnny Spill finished sixth and seventh respectively, ahead of Hideaki Nagai and Akito's brother Yoshito Watabe. Taylor Fletcher of the United States came in 10th.
FINAL STANDINGS (Jump/Run/Time/Loss)
1 Todd Lodwick 106.3 (5.) 19:10.7 (1.) 19:39.7
2 Bernhard Gruber 113.5 (1.) 19:40.1 (7.) +0:00.4
3 Tomaz Harp 99.5 (11.) 19:31.0 (4.) +0:47.3
4 Akito Watabe 106.5 (4.) 20:14.3 (15.) +1:02.6
5 Yusuke Minato 100.3 (10.) 20:03.7 (12.) +1:17.0
6 Christoph Bieler 96.4 (13.) 19:54.4 (11.) +0:48.0
7 Johnny Spill 92.0 (15.) 19:38.1 (6.) +1:24.4
8 Hideaki Nagai 100.5 (9.) 20:14.2 (14.) +1:26.5
9 Yoshito Watabe 111.4 (2.) 21:00.9 (22.) +1:19.2
10 Taylor Fletcher 91.7 (16.) 19:42.5 (8.) +1:29.8
