This study aimed to assess knowledge about non-pharmacological pain-relief methods in labor among women who have given birth at least once. This cross-sectional study was conducted using an online survey among 466 adult women. The minimum sample size was estimated based on the number of labor admissions in the year before the study in Poland. The survey included questions about respondents’ sociodemographics and knowledge of pain-relief methods. The knowledge score was calculated using the sum of correct answers. Non-parametric Spearman’s correlation, Kruskal–Wallis and Wilcoxon variance tests were used. Antenatal classes (313/68.9%) and the Internet (248/54.6%) were the most common sources of knowledge. The most popular pharmacological pain-relief methods included epidural anesthesia (386/85.0%) and nitrous oxide (301/66.3%). Massage and breathing techniques were the most commonly known non-pharmacological methods (405/89.2% and 400/88.1%, respectively). The knowledge score about non-pharmacological methods was significantly higher as compared to the pharmacological methods score (rc = 0.85; p < 0.001). Respondents’ age correlated with knowledge about non-pharmacological methods (rs = −0.10, p = 0.026) but did not correlate with knowledge about pharmacological methods. Educational level correlated with knowledge about pharmacological (rs = −0.13, p = 0.007) and non-pharmacological (rs = 0.14, p = 0.003) methods concerning pain relief in labor. No correlation was found between respondents’ knowledge and gravidity, number of vaginal or cesarean deliveries, and hospital referral levels for previous deliveries. Our findings support the need to implement educational programs to increase evidence-based knowledge about pain-relief methods during labor in women.