Volitional help sheets use Gollwitzer's (1993) concept of implementation intentions as a vehicle to change behaviour using Prochaska and DiClemente's (1983) processes of change. The present study designed and tested a volitional help sheet to increase physical activity in a group with low socioeconomic status (low-SES). Sixty-eight people (33 women, 35 men; mean age 27) with low-SES were randomly allocated to either an experimental group or a control group. Both groups received a questionnaire and a volitional help sheet; the only difference between the experimental and control groups was that the former were given explicit instructions to link occasions on which they were tempted not to be physically active with appropriate behavioural responses (processes of change). Physical activity (Metabolic Equivalent minutes per week) was the main outcome measure; behavioural intention and self-efficacy were the secondary outcome measures. The findings revealed significant increase in physical activity in the experimental condition, relative to the control condition, F (1, 66) = 7.28, p < 0.01, η2(10) = 0.10, but no differences for social cognitive variables. Furthermore, the participants who were most responsive to the intervention engaged in more than three times the physical activity at baseline than those who received the intervention but did not subsequently change. The findings provide further support for volitional help sheets to change health behaviour and extend them to a group with low-SES. Further work is required to refine this intervention tool.