Cellulose nanocrystal nanocomposites (CNC) with metallic nanoparticles (NP) are used for applications ranging from environmental remediation to smart electronics such as conductive films. To optimize the density of metallic NPs on the surface of the CNCs, NP size and concentration within the suspension should be controlled. This work shows the preparation of size-limited silver nanoparticles with the pulse synthesis process (PSP) method, effects of control parameters within the PSP method, and effects of the in situ addition of cellulose nanocrystals resulting in the attachment of silver nanoparticles (AgNPs). Our work incorporated the continuous addition of precursor to extend the growth stage, similar to the extended LaMer mechanism. Additionally, we integrated capping of the particles intermittently during the nucleation and growth processes. The resulting nanocomposite colloids consisted of AgNPs with maximum average size of 32 nm and attachment to CNCs.