Microalgae are rich in several bioactive compounds, among which carotenoids are particularly prominent. Carotenoids are lipophilic pigments with multiple biological effects, such as anti-inflammatory, antioxidant, anti-diabetic, and anti-obesity activities. Given the global prevalence of overweight and obesity as major health issues and the low adherence of patients to conventional treatment strategies, naturally occurring bioactive compounds present a promising approach to address obesity and its associated comorbidities. An inverse relationship between serum carotenoids levels and both BMI and metabolic syndrome prevalence has been observed. In addition, carotenoid supplementation has demonstrated anti-obesity effects in clinical trials and preclinical studies, although much more research is required. In this chapter, information about carotenoids occurrence, metabolism and distribution has been collected. Additionally, this review summarises current knowledge regarding the potential use of the most abundant carotenoids in microalgae (astaxanthin, β-carotene, fucoxanthin, lutein, lycopene, β-cryptoxanthin, and zeaxanthin), both in isolation and in combination, for obesity treatment, along with their primary mechanisms of action.