This review aims to assess and synthesize the recent scientific literature on bioactive phytochemicals derived from Cyanobacteria and microalgae, with a focus on their pharmaceutical and nutraceutical applications. A total of 837 articles published over the past seven years were retrieved from multiple databases, including studies reporting antioxidant, anti-inflammatory, antimicrobial, and other pharmacological and nutritional properties. After applying defined inclusion and exclusion criteria, 86 studies were selected for detailed analysis. Among these, 28% focused on nutritional and dietary applications, 26% on antioxidant activities, 22% on other pharmacological potentials, 13% on antimicrobial effects, and 11% on anti-inflammatory properties. The most frequently studied genera were Arthrospira/Limnospira (Cyanobacteria) (29 articles), followed by Chlorella (Chlorophyta) (13), Nannochloropsis (10), and Phaeodactylum (Bacillariophyceae) (8). Regarding the types of products studied, crude extracts or biomass were the most common (68.96%), followed by pigments (10.34%), lipids (8.04%), proteins (6.89%), and polysaccharides (5.74%). In terms of methodology, 72% of the studies employed in vitro approaches, with 42% using non-cellular assays and 30% using cellular assays, while in vivo and in silico approaches were used in 23% and 5% of studies, respectively. The available literature indicates that Cyanobacteria- and microalgae-based products are a promising source of bioactive compounds for pharmaceutical and nutraceutical applications. However, as most of the current evidence remains preliminary and derived largely from in vitro studies, these findings should be regarded as an early indication of potential that requires further in vivo and clinical validation.