Police in Nam Hong Linh Ward said the reptile was identified as a Chinese water dragon (Physignathus cocincinus), a protected species classified as endangered in Vietnam.
The animal was handed over by Le Hai Quan, 40, who found it and reported it to authorities.
Police have transferred the lizard to local forest rangers for a health assessment. It will be released back into the wild if deemed fit.
Authorities said the voluntary handover helped support biodiversity conservation and wildlife protection efforts.
They also urged residents who encounter wild animals in residential areas, or discover animals being illegally captured or kept, to notify police or forest rangers instead of buying, transporting, keeping or killing them.