In this study, a field experiment was conducted to examine the effects of requesting a donation following a pay rise announcement. The experiment evaluated the effects of (1) unexpectedly requesting a donation either immediately after the pay rise announcement or a week after the announcement, and (2) informing the workers in advance about the forthcoming request for a donation. First, the likelihood of donation increased when the request was made soon after the pay rise announcement, compared with the situation in which workers did not receive a pay rise but received the same final wage. The likelihood of donation was reduced when the workers were asked for a donation a week after the pay rise announcement rather than immediately. These findings may be explained by either mood changes or mental accounting. Second, alerting the workers who were promised a pay rise to the forthcoming request a week earlier significantly reduced donations compared with an unexpected request. This finding suggests that subjects used the additional time to find excuses to donate less.