Although non-proliferative lupus nephritis (LN) (class I, II or V) has been considered as a less severe type of LN, data on long-term renal prognosis are limited. We investigated the long-term outcomes and prognostic factors in non-proliferative LN. We retrospectively reviewed patients with systemic lupus erythematosus who were diagnosed with LN class I, II, V, or II + V by kidney biopsy from 1997 to 2021. A poor renal outcome was defined as an estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m2. We included 71 patients with non-proliferative LN (class I = 4; class II = 17; class V = 48; class II+V = 2), and the overall rate of poor renal outcomes was 29.6% (21/71). The univariate analysis indicated that older age, low eGFR at 6 or 12 months, failure to reach complete remission at 6 months, and LN chronicity score > 4 or activity score > 6 were significantly associated with poor renal outcomes. The multivariate analysis revealed that low eGFR at 6 months (HR 0.971, 95% CI 0.949-0.991; p = 0.014) was significantly associated with poor renal outcomes. Poor renal outcomes occurred in approximately 30% of patients with non-proliferative LN after long-term follow-up. More active management may be needed for non-proliferative LN, especially for patients with eGFR < 60 mL/ min/1.73 m2 at 6 months follow-up after LN diagnosis.