The effect of Farm Assurance (FA) assessors’ attitude to farm animal welfare on the inter-observer reliability of some welfare outcome measures achieved following training was investigated as part of a larger project examining the feasibility and benefits of the incorporation of some on-farm welfare outcome assessments into UK Pig Farm Assurance Schemes. A total of thirty-one FA assessors were trained in three training sessions to assess the following welfare outcome measures: body lesions, tail lesions, severe tail lesions, lameness and pigs requiring hospitalisation. Assessment of photographs, live observations of individual pigs and pens of pigs were used to generate inter-observer reliability data. A previously validated farm animal welfare questionnaire was used to assess the FA assessors’ attitudes to farm animal welfare. Principal Component Analysis of FA assessor scores for this questionnaire resulted in two major components, with component 1 termed ‘pigs have mental welfare’ and component 2 termed ‘people-centric, pigs as profit’. FA assessors demonstrated a range in attitudes to farm animal welfare and, when assessing the same pigs, recorded a range in prevalence of welfare outcome measures and degree of agreement with a gold standard following training. There were only seven out of a possible 98 significant correlations between the FA assessor scores for components 1 and 2 and their recorded prevalence of welfare measures and levels of agreement with a gold standard. In particular, FA assessors’ scores for component 1 were significantly positively correlated with the recorded prevalence for pigs requiring hospitalisation in two of the three training sessions although there was no effect on the agreement with a gold standard for this measure. These results indicate that training in welfare outcomes, defined by a standard protocol, is relatively unconfounded by observer attitudes to farm animal welfare. To obtain better levels of agreement between assessors, and therefore more reliable data, it is recommended that FA schemes concentrate their resources on providing good quality training in a well-defined protocol and reliability testing and that they do not need to attempt to account for the attitudes of the FA assessors to farm animal welfare.