He was appointed magister equitum in 357, but fell out of favour when he refused to side with Julian when the army declared him Augustus.
During the reign of Emperor Constantius II, Lupicinus was named magister equitum (commander of cavalry) in 357.
In one instance, he devised a successful plan whereby 300 Roman troops secretly crossed the Rhine at night and attacked the Alemannic camp on the opposite bank.
This allowed the main body of Julian's army to cross and quickly defeat and accept the surrender of the five confederated Alemannic kings.
Lupicinus was Emperor Valens' senior commander against the rebel troops holding Asia Minor.