Background and Purpose: Early mastitis symptoms including redness, swelling, pain, breast lump, general malaise, and breast engorgement may reduce the willingness of mothers to breastfeed and cause early breastfeeding cessation. The assessment tools for assessing early mastitis symptoms include subjective and objective measures. However, limited evidence exists to assess whether the patient-reported subjective measures correlate to objective measures in women with early mastitis. Therefore, the purpose of this study was to investigate the correlation between subjective and objective measures of early mastitis symptoms in lactating women. Methods: Lactating women, aged 21 to 45 years, with early mastitis symptoms were recruited from a medical center and postnatal care centers during November 2020 to November 2021. The patient-reported subjective measures of symptoms included (1) redness and swelling (visual analogue scale, VAS), (2) pain (VAS), (3) thickening of breast tissue, or a breast lump (VAS), (4) general malaise (VAS), and (5) severity of breast engorgement (six-point engorgement scale). The objective measures included breast temperature measured using non-contact infrared thermometer and breast hardness measured using durometer. Statistical analysis was performed using Spearman's correlation analysis. A p-value of < 0.05 indicated a statistically significant correlation. Results: A total of nine participants (mean age: 32.33 ± 2.18 years; mean body mass index: 22.61 ± 2.82 kg/m^2) were recruited. Severity of breast engorgement was strongly correlated with redness and swelling (r_s = 0.770, p = 0.015), pain (r_s = 0.867, p = 0.002) and thickening of breast tissue, or a breast lump (r_s = 0.946, p < 0.001) and moderately correlated with general malaise (r_s = 0.678, p = 0.045). However, objective measures were not correlated with subjective measures. Conclusions: This study showed that there were moderate to strong correlations between the subjective measures of early mastitis symptoms. However, subjective and objective measures were not correlated. Future studies with larger sample size are needed to confirm the findings of this study and to validate the objective measurements of early mastitis symptoms. Clinical Relevance: Our findings suggest that both six-point engorgement scale and VAS could be used as clinical tools to assess the severity of early mastitis symptoms.