We report the seasonal variability of temperature, nutrients, and total and size fractionated chlorophyll- in nearshore waters off northern Baja California (nBC), under conditions of the marine heatwave and El Niño that occurred in the northeastern Pacific during 2014‑2015. Compared with 2008‑2012, our study period was characterized by warmer waters, nitrate-impoverished and with very low chlorophyll- concentration, which was closely associated with strong stratification and reduced upwelling conditions off nBC. Temperature anomalies were >3.0°C by the end of 2014 when the marine heatwave prevailed, decreased during the spring-early summer upwelling season of 2015, and returned to >3.5°C by the end of 2015 when El Niño appeared along the coast of nBC. As in 2008‑2012 and closely coupled with upwelling, a clear seasonal cycle of total chlorophyll- was recorded under these abnormally warm conditions. However, total chlorophyll- and nitrate concentrations were significantly reduced (25-68% and 33-90%, respectively), with negative anomalies throughout the study period. Moreover, the seasonal evolution of the size-fractionated chlorophyll- concentration showed that smaller cells (<5 mm) systematically contributed with the largest fraction (>60%) of the total chlorophyll-. Our findings indicate that the sequential occurrence of the marine heatwave in 2014 and El Niño in 2015, had a significant and sustained impact limiting the nitrate supply and reducing the total chlorophyll- in nearshore waters off nBC. In conclusion, our data reveal that a shift towards an oligotrophic state occurred in nearshore surface waters off northern Baja California during the warm period of 2014-2015.