Background: In anti-phospholipase A2 receptor (PLA2R) membranous nephropathy (MN) there is controversy whether spontaneous remission (SR) can be predicted using a single titre or by assessing the dynamic changes in anti-PLA2R antibody (ab) titres. The study objective was to identify the optimal dynamics of anti-PLA2Rab titres to predict SR in MN. Methods: A total of 127 nephrotic patients with anti-PLA2R-MN were prospectively followed up for 6 months under conservative treatment. Anti-PLA2Rabs and proteinuria were assessed at diagnosis and monthly thereafter. The primary endpoint (PEP) was a reduction of proteinuria ≥50% at 6 months. Logistic models with baseline and evolutive anti-PLA2Rab titres were developed to predict the PEP. Results: A total of 28 patients (22%) reached the PEP. These patients were more frequently female and had significantly lower baseline proteinuria and anti-PLA2Rab titres. An anti-PLA2R titre ≤97.5 RU/mL at diagnosis had a sensitivity of 71% and a specificity of 81% to predict the PEP. The model including baseline anti-PLA2Rabs and a reduction ≥15% at 3 months predicted the PEP with a sensitivity of 93% and a specificity of 80%, with an area under the curve that was significantly greater than that obtained with relative changes of proteinuria in the same period of time {odds ratio [OR] 0.95 [95% confidence interval (CI) 0.91–0.98 versus OR 0.79 [95% CI 0.70–0.88], respectively; P = 0.0013}. Conclusions: Combining the baseline anti-PLA2Rab titres with their relative changes at 3 months after diagnosis gives the earliest prediction for achieving a reduction of urinary protein excretion ≥50% at 6 months in MN, thereby shortening the observation period currently recommended to make individualized decisions to start immunosuppressive therapy.