Although the oil industry has evolved significantly, it is still considered a high-risk sector for workers. Special working conditions characterize this industry, including extended schedules and night shifts work in the oilfield. This study develops a cross-sectional analysis to determine the working conditions associated with the prevalence of mental stress among night-shift oil workers. For this purpose, a survey with items from the Goldberg GHQ12 questionnaire was applied to a sample of 159 workers in an oil company in the Ecuadorian Amazon. The collected data were analyzed using frequency tables, chi-square association tests and logistic regressions using the EPI INFO software. The results showed that workers aged between 20 and 35 years, with the machinist occupation and working in day-night rotational shifts, have a higher risk of suffering work-related stress (p-value < 0.05). In the other hand, ageing (> 50 years) has been identified as a protective factor against stress, with a risk reduction of up to 78% compared to younger workers (20–35 years). Workers performing well workover activities according to their age, occupation and shifts present a high prevalence of occupational stress, preventive measures are therefore necessary to improve their wellbeing.