Proteasome activity in ubiquitin‐proteasome pathway plays a pivotal role in degradation and clearance of aggregated, oxidized, damaged, and misfolded unwanted proteins to control protein homeostasis or proteostasis. Proteasome activity decreases with cellular senescence, aging, and age‐related diseases. Therefore, enhancement of impaired proteasome function by molecular biological and/or pharmacological intervention is an active area of research. Bryostatin‐1, a naturally occurring macrocyclic lactone, activates PKC isozymes (specifically, ‐α and ‐ϵ) at sub‐nanomolar concentrations, but downregulates at higher concentrations. Here, we present bryostatin‐1 increased chymotrypsin‐like proteasome activity of 20S assembly at sub‐nanomolar to nanomolar concentrations (0.3‐30 nM). However, proteasome activity decreased at a micromolar concentration of bryostatin‐1 (AG08044 cultured skin: P < 0.005; differentiated SH‐SY5Y cells: P < 0.02). Modulation of proteasome function by bryostatin‐1 was studied in six dermal fibroblast primary cell lines developed both from freshly taken biopsies from healthy donors (n = 2) and obtained from well‐characterized cell repositories (n = 4; without any diseases). Bryostatin‐1 enhanced proteasome activity in cultured skin fibroblasts obtained from banked and freshly isolated skin fibroblasts from skin biopsies at the sub‐nanomolar concentration (P < 0.015). Modulation of proteasome function by bryostatin‐1 was confirmed in neuron‐like differentiated SH‐SY5Y cells. Direct additions of bryostatin‐1 into cell lysates prepared from neuron‐like differentiated SH‐SY5Y, Jurkat cells, and cultured skin fibroblasts were unable to increase proteasome activity indicating that bryostatin‐1 can only modulate proteasome activity when added to live cell culture systems. Standard PKC inhibitors blocked bryostatin‐1 induced proteasome activity modulation suggesting that enhancement of proteasome activity was mediated by PKC modulation.