Lasogga will wear the Hamburg shirt until the end of the season and said he was "really looking forward to the challenge" of playing for Hamburg. The Germany U-21 striker missed a large chunk of last season with a cruciate ligament injury, but will begin training with his new team-mates on Tuesday.
"Exactly what we've been looking for"
HSV sporting Director Oliver Kreuzer was delighted with the capture of Lasogga, describing him as "exactly the type of striker we've been looking for". He will provide competition to and the in-form Jacques Zoua to lead the line for the Red-Shorts.
Lasogga, who has made 32 Bundesliga appearances and scored eight goals, said it wasn't "an easy decision to leave Hertha" but added that "he's excited about trying to impress the fantastic Hamburg fans".
Hamburg midfielder Per Skjelbred takes the opposite path to Lasogga, joining Hertha Berlin on loan for the 2013/14 season.