This project hosts Mime Initiation Latency (MIL) norms for 189 object photographs, developed to support research on motor affordances and embodied cognition. The dataset provides behavioural latency measures indexing the time required for participants to initiate a pantomimed object-use action in response to colour photographs drawn from the Bank of Standardized Stimuli (BOSS; Brodeur et al., 2010, 2014). MIL constitutes a behavioural motor norm intended to complement existing subjective affordance measures (e.g., manipulability, graspability, mimability, body–object interaction). The norms were collected from Thai undergraduate participants using a controlled reaction-time paradigm implemented in E-Prime. After data screening and trimming procedures, normative statistics (means, standard deviations, distributional indices) are reported for 189 manipulable object photographs. Construct validity was evaluated through correlational and regression analyses with established motor and psycholinguistic norms. MIL was moderately to strongly associated with conceptually related motor variables and weakly or not associated with conceptually unrelated motor or lexical-semantic variables, supporting its interpretation as a behavioural index of motor affordance. The repository contains: Aggregated MIL norms (item-level statistics), and Raw data (response times, in milliseconds, for each participant). The shared materials are intended to facilitate stimulus selection, replication, and secondary analyses involving behavioural motor variables. This dataset accompanies the article: Ludington, J. D., & Clarke, A. J. B. (in press). Mime Initiation Latency for Object Photographs: A Behavioral Motor Norm. Journal of Psycholinguistic Research. Full bibliographic details (volume, issue, pages, DOI) will be added upon publication. The norms are released under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence to facilitate reuse with appropriate attribution.