Excited state absorption‐induced up conversion at 452 and 480 nm in Tm:Eu:ZBLAN fiber was observed for a single pump laser source at 650 nm. Compared to Tm:ZBLAN fiber, codoping with Eu3+increases the 452 nm emission while the 480 nm emission is reduced. The effective lifetime of the terminal3H4level of the 452 nm transition in Tm3+is shortened by energy transfer to the7F6level in Eu3+. This energy transfer scheme is useful in discriminating radiative transitions.