<b><i>Objectives:</i></b> Although splenectomy has long been second-line option for immune thrombocytopenia (ITP) patients, an indicator that reliably predicts the efficacy of splenectomy is still being explored. We investigated the treatment outcomes of splenectomy as a second-line therapy for relapsed/refractory ITP according to first-line intravenous immunoglobulin (IVIG) responses. <b><i>Methods:</i></b> Fifty-two adult patients treated with splenectomy as second-line therapy for ITP between 2009 and 2019 were included, and they were classified according to first-line IVIG responses (no response to IVIG: nonresponders; only transient IVIG response shorter than 4 weeks: poor responders; IVIG response for a longer period; stable responders). The efficacy of splenectomy was analyzed in the three subgroups. <b><i>Results:</i></b> Of the 52 patients, 10 were IVIG nonresponders, 34 were poor responders, and the remaining 8 were stable responders. Response to splenectomy was observed in 50.0% of IVIG nonresponders, 94.1% of poor responders, and 100% of stable responders (<i>p</i> = 0.0030). Among the 45 patients who responded to splenectomy, 51.1% relapsed subsequently, and a significantly lower relapse rate was noted in the stable IVIG responders (12.5%, <i>p</i> = 0.0220) than in nonresponders (60.0%) and poor responders (59.4%). <b><i>Conclusions:</i></b> First-line IVIG response is indicated as a useful predictive factor for response to splenectomy.