This work was aimed to evaluate the performance of two different surface modifications on cellulose nano-particles obtained from blue agave bagasse. Cellulose nanofibers were obtained from traditional mechanical methods, and cellulose nanocrystals were obtained via sulfuric acid hydrolysis. After cellulose extraction and size reduction, different composites were elaborated using poly(lactic acid) as matrix varying fiber concentrations and using cellulosic particles of diverse size and surface modification (3-aminopropyl triethoxysilane silanized cellulose nanofibers and dodecanoyl chloride esterified cellulose nanocrystals). Non-cellulosic elimination and the effect of surface modifications were analyzed with infrared analysis, showing characteristic intensities for cellulosic species and new peaks for each modification (characteristic ester peak ∼1740 cm−1, and amino peak ∼1550 cm−1) cellulose nanofibers and nanocrystals were observed with atom-force microscopy; crystallinity of nano-scale cellulose before and after modifications was obtained with X-ray diffraction to analyze the performance of the modifications. Composites were tested with stress–strain standard methods showing better mechanical properties when surface modifications were performed and the amount of filler was 0.5 wt% reaching an increase in strain to fracture of more than 20%.