Purpose: The aim of the present work is to assess the Objective Breast Cosmesis Scale (OBCS) in a patient cohort that was treated in two hospitals. Their treatment-related cosmetic changes were recorded on nonstandardized photographs. Methods and Materials: Nineteen female patients were enrolled in two radiation oncology centers (Nice, France, and Perugia, Italy). All patients had undergone breast-conserving surgery (BCS) and received adjuvant accelerated partial breast irradiation using interstitial fractionated multicatheter high-dose-rate brachytherapy. One photograph before and another after accelerated partial breast irradiation was taken for each patient to record changes in breast cosmesis. Using the OBCS, before and after photographs were analyzed by measuring distances between anatomic features. OBCS scores from four doctors (two males [one radiation oncologist and one post-grad trainee] and two females [one radiation oncologist and one post-grad trainee]) were compared. Results: Agreement was high between trainees and specialist, and males and females before and after treatment. The intraclass correlation coefficient ranged from 0.867 to 0.950 before treatment and from 0.876 to 0.952 afterward. The coefficient of variation ranged from 12% to 26.5% before treatment, and from 13% to 21.4% afterward. Conclusions: The OBCS is easy, time-efficient, reproducible, cost-effective, and reliable. Its potential practical applications merit further investigation in future studies.