Background: Hookwire localization (HWL) is the gold standard for localizing impalpable tumours for breast conserving surgery. An alternative technique, radioguided occult lesion localization using iodine-125 seeds (ROLLIS), has been associated with lower re-excision rates. This paper investigates if cosmetic outcomes differ in women undergoing breast conserving surgery with HWL or ROLLIS. Methods: Women who had ROLLIS or HWL guided excision for impalpable breast cancer within a multicentre randomized controlled trial (RCT) (ANZCTR 12613000655741) were recruited. Exclusions were level 2 oncoplasty and mastectomy. Cosmetic outcome was calculated using BCCT.core, the Hopwood Body Image Scale and estimated percentage breast volume excised. Chi-squared analysis was used to determine the difference between the intervention groups. Results: Analysis was performed for 123 participants (66 ROLLIS and 57 HWL). The cosmetic outcome determined by BCCT.core for all participants was good with no significant difference between the ROLLIS and HWL groups. When reviewing the number of patients who experienced either a good or excellent result, there was a significantly higher number of patients in the ROLLIS group (n = 53, 82%) compared to the HWL group (n = 42, 74%, P = 0.02. There were no differences in Hopwood Body Image Scale or estimated percentage breast volume excised between groups. There was a reduction in the frequency of re-excision in the ROLLIS group (n = 3, 4.5%) versus HWL group (n = 8, 14%); however, this was not significant (P = 0.06). Conclusion: Pre-operative localization of impalpable breast lesions using either ROLLIS or HWL resulted in a good cosmetic outcome with no significant difference between localization techniques.