The COVID-19 pandemic constituted a disruptive global event that significantly impacted emotional states, psychological well-being, and cognitive functioning across diverse populations. This chapter analyzes these three interconnected domains through a systematic literature review conducted according to PRISMA guidelines. An initial search yielded 1404 articles across six major academic databases. After applying defined inclusion and exclusion criteria, a final sample of 40 empirical studies was selected for qualitative synthesis. The results are presented in three thematic categories. First, emotional state: the pandemic elicited intense negative emotions such as fear, sadness, anger, and anxiety, particularly during its early stages. Younger individuals, students, and those using maladaptive coping strategies were most affected. Over time, however, emotional trajectories showed signs of adaptation, with gratitude, hope, and emotional coherence emerging as protective emotional traits. Second, psychological well-being: multiple studies reported declines in well-being, particularly among adolescents, students, women, and vulnerable populations. Increases in depression, anxiety, loneliness, and suicidal ideation were common. However, certain groups—especially older adults—exhibited resilience and emotional stability. Predictors of well-being included age, gender, income, coping mechanisms, daily routines, and access to social support. Third, cognitive processes: the pandemic disrupted cognitive functions such as appraisal, attention, emotion regulation, memory, and decision-making. Maladaptive cognitive patterns, including catastrophic thinking and perceived helplessness, were linked to greater psychological distress. In contrast, adaptive strategies such as cognitive reappraisal, functional problem-solving, and positive social connections were associated with improved outcomes. Cognitive consequences also included memory distortions, spontaneous thought disruptions (e.g., mind-wandering, dreaming), and decision-making impairments. In conclusion, the pandemic generated a complex psychological impact. Emotional, well-being, and cognitive responses varied across individuals and contexts, highlighting the need for integrated and personalized mental health strategies during and after collective crises.