This study aimed to examine the relationship between Korean fathers' work-family strains and gains and marital satisfaction and to validate the mediating effect of parenting stress in the relationship. This study used the 14th-year survey data of the Panel Study of Korean Children (PSKC) conducted by the Korea Institute of Child Care and Education (KICCE), the latest available data. The PSKC is a longitudinal study of children's growth and development from birth in the Republic of Korea. After excluding datasets containing missing values from the data collected from 2150 respondents, the data were extracted from the survey responses collected from 1130 respondents, and descriptive statistical analysis, path analysis, and mediating effect analysis were conducted. First, Korean fathers' work-family strains had a positive (+) influence on parenting stress (β = 0.658, p < 0.001). Second, Korean fathers' work-family strains had a negative (-) influence on marital satisfaction (β = -0.185, p < 0.001). Third, Korean fathers' work-family gains did not have a statistically significant influence on parenting stress (β = 0.016, p = 0.632). Fourth, Korean fathers' work-family gains had a positive (+) influence on marital satisfaction (β = 0.381, p < 0.001). Fifth, Korean fathers' parenting stress did not have a statistically significant influence on marital satisfaction (β = 0.011, p = 0.783). Sixth, the indirect effect of work-family strains on marital satisfaction via parenting stress (β = 0.013, 95% Bias-corrected CI = -0.042∼0.075) was statistically significant, and specifically, it had a partial mediating effect. Seventh, the indirect effect of work-family gains on marital satisfaction via parenting stress (β = 0.028, 95% Bias-corrected CI = 0.005∼0.051) was statistically significant, and specifically, it had a partial mediating effect. This study aims to provide the basic data for various family support policies for fathers by understanding the current status of work-family balance for fathers in modern society, as well as by examining the effects of parenting stress in the relationship with marital satisfaction.