COVID-19 impacted the childbirth experience and increased the rates of postpartum depression (PPD). We assessed the longitudinal effects of the pandemic on the rates of PPD and evaluated the PPD causes and symptoms among women who delivered during the first COVID-19 quarantine in Israel. The participants completed online questionnaires 3 (T1) and 6 months (T2) following delivery. We used the ‘COVID-19 exposure’ questionnaire, while PPD symptoms, situational anxiety, and social support were evaluated with the EPDS, STAI, and MSPSS questionnaires. The mean EPDS scores increased between T1 and T2 (6.31 ± 5.6 vs. 6.92 ± 5.9, mean difference −0.64 ± 4.59 (95% CI (−1.21)–(−0.06)); t (244) = −2.17, p = 0.031), and the STAI scores decreased (45.35 ± 16.4 vs. 41.47 ± 14.0, t(234) = 4.39, p = 0.000). Despite the exposure to an increased number of COVID-19 events (3.63 ± 1.8 vs. (6.34 ± 2.3)), the impact of exposure decreased between T1 and T2 (8.91 ± 4.6 vs. 7.47 ± 4.1), p < 0.001). In the MSPSS, significant differences were noted on the family scale between the T1 (6.10 ± 1.3) and T2 (5.91 ± 1.4) scores; t (216) = 2.68, p = 0.0008. A regression analysis showed three statistically significant variables that correlated with increased EPDS scores: the MSPSS family subscale (F (1212.00) = 4.308, p = 0.039), the STAI scores (F (1212.00) = 31.988, p = 0.000), and the impact of exposure to COVID-19 (F (1212.00) = 5.038, p = 0.026). The rates of PPD increased for women who delivered during the first COVID-19 lockdown. Further research is warranted to help reduce PPD among these women.