Bombyx mori L. nanofibroin has potential as an organic filler composite restoration because it has excellent mechanical and functional strength. One of the main requirements of the restoration material is to have good mechanical strength to wear resistance of dental restorations as well as tooth wear or antagonist restorations. The mechanical properties of microhardness are essential to study as a preliminary study in the new material. The aim of this study were to find out the nanofibroin potency as composite resin filler and to compare the microhardness of nanofibroin and nanofiller composites as gold standart. Methods: Nanofibroin particles were extracted from Bombyx mori L. cocoon by degumming, dissolving, dialysis and sonification. The nanofibroin filler weight was determined using volume fraction of natural fibers and mixed with an organic matrix. Three of sample groups were divided into nanofibroin composites, nanofiller composites (Z350 XT flowable 3M ESPE) as a positive control and composites without fillers as negative control. Microhardness was measured using a microhardness tester (Shimadzu, Japan). Data were analyzed using Kruskal Wallis test. Results: The nanofibroin composite have the highest microhardness (146.45), while nanofiller has a microhardness of (110.40 VHN) and the composite without filler has the lowest microhardness (31.55 VHN) and the statistical analysis showed p>0.05 level of significance. Conclusion. The Bombyx mori L. nanofibroin has potential for composite filler restoration eith better microhardness than positive control.