Nanomaterials biogenic approaches of synthesis exceed chemical ways in simplicity, toxicity and generation of homogeneous colloidals. Herein, a rare approach for biosynthesis of SeNPs is described where a rapid myogenic method was applied. The endophytic fungus isolate, Asperigillus terrus H1 with accession no. PQ550684, that isolated for the first time from Rumex thyrsiflorus was used for the bio-reduction of sodium selenite contained in the growth medium to produce selenium nanoparticles. Change in color of the culture medium to orange-red signifies the formation of nano-selenium. DLS, TEM and ICP-OES techniques demonstrated the formation of monodispersive amorphous selenium nanoparticles with average hydrodynamic size of 55.76 nm with -25.6 particles charge. The synthesized SeNPs were checked for their in-vitro cytotoxicity against normal human lung fibroblast cells (MRC-5) and human lung adenocarcinoma cell line (A549) which giving IC50 of 485.16±13.71 and 196.25± 4.23 µg/ml respectively. Their ability to be applied in biomedical applications was studied in-vivo through labeling them with 99mTc and tracing their distribution in normal and tumor-bearing mice. The produced mycogenic SeNPs showed excellent physical and biological characteristics that could make them a promising nanoplatform for tumor molecular imaging.