Scalp-recorded event-related potentials (ERPs) are among fundamental research tools for cognitive brain activity at a high temporal resolution. Orienting to new, unexpected or unpredictable stimuli is an involuntary shift of attention that is a way of alerting to potentially significant environmental events. The novelty paradigm in cognitive electrophysiology is an experimental design, in which the effects of novel stimuli on brain electrical activity are measured using unexpected and ever-changing novel non-target stimuli interspersed in the set of standards and targets in the classical oddball paradigm. The typical ERP component obtained during the novelty paradigm is an N2-P3a complex occurring in response to novel non-targets, where the P3a is a positive wave around 300 ms after the stimulus and has a more centro-frontal topography in contrast to the parietal P3b of the target responses. The P3b potential is related to selective or voluntary attention and memory updating processes, while P3a potential is assumed to reflect passive, involuntary switching of attention or orienting. The aim of this study is to investigate the effects of selective attention on the involuntary attention switching in humans. Twenty-one healthy volunteers (ages between 19 and 24 years) participated in the study. ERPs were recorded with 30 electrodes (international 10/20 system) using an auditory novelty paradigm. Intervals between target and novel stimuli were randomly changed at 4, 6, 10, and 14 s. Obtained ERP trials from the responses to novel stimuli were separately averaged in each interval period. The amplitudes and latencies of N2 and P3a responses were measured for each interval period. The differences among the four intervals were statistically tested with repeated measures analyses of variance (ANOVA). Statistical analyses indicate that the amplitudes of N2 and peak-to-peak amplitudes of P3a were significantly higher in the ERP trials with shorter target-novel intervals (p<0.005 and p<0.001, respectively). However, this interaction was not observed for the latencies of N2 and P3a potentials (p>0.05). Our results suggest that selective attention modulates involuntary attention switching in humans.