Background/Purpose: Organisational culture is a key determinant of employee job satisfaction and labour productivity in Nigerian financial institutions, yet the sociological mechanisms through which culture shapes these outcomes, particularly the mediating role of job satisfaction, remain underexamined. Objectives: This study examines the relationships among organisational culture, job satisfaction, and labour productivity in Nigeria's banking and insurance sectors from an Industrial Sociology perspective, focusing on the mediating role of job satisfaction. Design/Methodology: A descriptive survey design, underpinned by a post-positivist epistemological orientation, was adopted. A structured questionnaire drawing on the Organisational Culture Assessment Instrument (OCAI), the Minnesota Satisfaction Questionnaire (MSQ), and established productivity measures was administered to 383 respondents (response rate = 96.0%) from 14 financial institutions across Lagos, Port Harcourt, Abuja, and Kano, using stratified random sampling. Data were analysed using descriptive statistics, Pearson correlation, hierarchical multiple regression, and Structural Equation Modelling (SEM) with bootstrapped mediation procedures (5,000 samples). Findings: Organisational culture significantly and positively influences both job satisfaction (β = .587, p < .001) and labour productivity (β = .321, p < .001). Job satisfaction significantly predicts labour productivity (β = .412, p < .001) and partially mediates the culture–productivity relationship (indirect β = .242, 95% BC CI [.171, .321]; proportion mediated = 43.0%). Employee Involvement, Communication Culture, and Reward and Recognition Culture were the three strongest predictors of job satisfaction, while Leadership Culture and Innovation and Adaptability Culture demonstrated the strongest direct effects on labour productivity. Practical Implications: Nigerian financial institutions must invest in participatory, transparent, and employee-centred organisational cultures to sustain workforce productivity. Originality/Value: This study advances Industrial Sociology scholarship by establishing job satisfaction as an empirically confirmed mediating mechanism in the culture–labour productivity relationship in the Nigerian financial sector. Keywords: Organisational Culture, Job Satisfaction, Labour Productivity, Industrial Sociology, Nigerian Financial Institutions, Employee Performance, Workplace Relations, Social Exchange