The study’s objective was to investigate the associations between workplace conflicts and self-reported sickness presenteeism defined as going to work while being ill. Cross-sectional survey data pooled from four national surveys in years 2006, 2010, 2013 and 2018 with a study sample of 6368 employees (mean age 42.9 years and 52.9% females) were used. Respondents were randomly drawn from different regions and industries; therefore, the sample is representative of the working population of Latvia. The computer-assisted personal interviewing (CAPI) method was used to collect data at respondents’ places of residence. The associations between conflicts in the workplace and presenteeism were analyzed by using binomial logistic regression and calculated as odds ratios (ORs) with 95% confidence intervals (CIs) adjusted (aOR) for gender, age, education, and survey year. On average, 11% of respondents reported sickness presenteeism during the last year. The odds of presenteeism significantly increased for all types of workplace conflicts, but most for conflicts with managers (OR = 2.84). The odds of presenteeism doubled for those reporting conflicts with other employees (OR = 2.19) and conflicts with customers (OR = 1.85). The odds of sickness presenteeism were significantly higher if the workplace conflicts occurred often (seven times for conflicts between managers and employees, and four times for conflicts with customers) and with other employees. Presenteeism frequency increased more than three times if respondents had more than two types of conflict at work. The results of this study show that having any type of conflict in the workplace significantly increases the frequency of sickness presenteeism, especially when conflicts are frequent or an employee has more types of conflicts in the workplace. The study results justify the need to implement targeted and effective workplace conflict management measures at the organizational level to decrease sickness presenteeism.