Previously, external beam radiotherapy (RT) was utilized less frequently for HCC due to concerns for excess dose to uninvolved liver in patients (pts) with baseline liver dysfunction. IMPT, however, offers the ability to treat HCC with a high dose of often hypo-fractionated RT, while minimizing dose to the remaining healthy liver. Limited data exists on outcomes for pts with unresectable HCC treated with IMPT. We present the initial acute toxicity and short-term survival results for the cohort of HCC pts treated with IMPT on our two campuses. A retrospective review was conducted on all pts who underwent IMPT treatments for unresectable HCC from 2015 to 2018. Pts were excluded if they did not complete the planned RT course. Patient, treatment, toxicity, and outcome characteristics were extracted from electronic medical records. Frequency (%) for categorical variables and median values (interquartile range [IQR]) for continuous variables were calculated. Outcomes (progression free [PFS] and overall [OS] survivals) were determined using Kaplan-Meier methods. Thirty-one (31) pts were included. Median follow-up was 11 (IQR, 5-12) months. This cohort had the following baseline characteristics: male (65%); white (84%); ECOG 0-1 (80%); primary liver disease etiology (hepatitis C 22%, alcohol 22%, and NASH 35%); diagnosed cirrhosis (68%); Child-Pugh (CP) A 5-6 (68%), CP-B 7-9 (32%); and prior liver-directed therapies (LDT, 61%). Of those who had prior LDT’s, the median number of procedures was 2 (TACE 45%, bland embolization 26%, RFA 23%). The targeted tumors for IMPT had the following characteristics: median size 4.7 (IQR, 3.1-5.9) cm; vascular thrombosis (39%); and being locally recurrent (58%). The most common RT fractionation was 58.5 Gy and 67.5 Gy in 15 fractions (39% each). Five pts (16%) underwent stereotactic body radiotherapy with 37.5 (1 pt) and 50 Gy (4 pts) in 5 fractions, respectively. IMPT was well-tolerated, with only one (3%) acute grade 3 toxicity (pain) and three (10%) grade 2 toxicities (nausea, pain, and anorexia). At the time of first follow-up after IMPT (median 2.5 months), 5 (16%) pts experienced an increase in CP by 2 points. At the time of this analysis, 7 (10%) pts experienced tumor progression locally, 14 (45%) pts had tumor growth elsewhere in the liver, 5 (17%) pts developed distant metastases, and 12 (39%) pts had died. At one-year’s mark, PFS was 31% and OS was 78%. While this cohort of HCC pts tends to have increased number of prior LDT’s and poorer baseline health status, our experience shows that IMPT is a well-tolerated treatment, with limited effects on liver function and promising short-term outcomes. Further prospective investigation of IMPT for treatment of unresectable HCC and guidance for patient selection are warranted.