Employers’ knowledge and awareness about autism can be a key barrier to autistic people obtaining employment, yet there is a dearth of literature examining interventions that focus on employers. The current study was an initial evaluation of the efficacy of an online autism training programme, Understanding Autism in the Workplace, in changing employers’ autism knowledge and commitment to inclusion in the workplace. Employers (N = 129) from 22 organisations in the United Kingdom completed the training with an autistic (n = 45) or non-autistic (n = 84) trainer. Participants completed surveys measuring (a) autism knowledge and (b) commitment to inclusion in the workplace, before and after the online training. Results showed that at a group-level, autism knowledge and commitment to inclusion in the workplace improved from before training to after training for all participants with an autistic and a non-autistic trainer. This latter result may be attributable to the training being co-designed by autistic people (i.e., there was autistic input in the course irrespective of whether the trainer delivering the session was autistic or not). At an individual-level, however, only a minority of participants showed a statistically reliable increase in autism knowledge (10.1%), and commitment to inclusion in the workplace (5.8%). These results suggest autism training was more effective for some participants than others. Autism training should not, therefore, be relied upon as the sole initiative to address barriers to employment for autistic people, but instead should be part of a broader package of support for employers.