Introduction: The lymphoid infiltrate has shown a prognostic impact in several tumors. No study focused on intrahepatic mass-forming cholangiocarcinoma (MFCCC). Methods: All consecutive patients undergoing surgery for MFCCC between 2005 and 2015 were considered. The inclusion criteria were complete resection and follow-up ≥12 months. Patients with operative mortality were excluded. Tissue sections from MFCCC were immunostained for CD3+, CD4+, CD8+, Foxp3+ and CD68+. Results: Overall, 53 patients were analyzed. MFCCC were multiple in 10 patients, >50 mm in 26, and N+ in 12. At univariate analysis, the following lymphoid infiltrate values had a prognostic impact: CD3+ >0.10% (overall survival, OS p< 0.001, recurrence-free survival, RFS p< 0.001); CD8+ >0.10% (OS p=0.044, RFS p=0.001), CD4+ >0.30% (OS p=0.094, RFS p=0.009), and Foxp3+ present (OS p=0.097). At multivariable analysis, CD3+ value was a prognostic factor of OS and RFS [>0.10%, 5-year OS 66.9% vs. 18.2% if ≤0.10%, HR=0.287, p=0.049; 3-year RFS 48.1% vs. 9.1%, HR=0.232, p=0.001] and Foxp3+ was a prognostic factor of OS [present, 5-year OS 21.4% vs. 61.9% if absent, HR=2.924, p=0.044].CD3+ values stratified prognosis in T1 patients (5-year OS 73.9%/14.3%, p< 0.001; 3-year RFS 60.8%/14.3%, p< 0.001), in N+ patients (OS 71.4%/0%, p=0.028; RFS 42.9%/0%, p=0.011) and in patients without lymph-node metastases (RFS 49.7%/20.0%, p=0.062). Conclusions: The lymphoid infiltrate impacts prognosis of MFCCC after complete surgery. CD3+ infiltrate is associated with higher survival and lower recurrence risk, while Foxp3+ is associated with worse prognosis. CD3+ infiltrate allows to refine prognosis in early tumors and across different N stages.