Neurofeedback, the self-regulation of brain signals recorded using Electroencephalogram (EEG), allows Brain-Computer Interface (BCI) users to enhance cognitive as well as motor functions using specific training strategies. Therapeutic effects of neurofeedback (by the induction of neuroplasticity) on treatment of people with neurological disorders such as Attention-Deficit Hyperactive Disorder (ADHD), dementia and stroke have been reported in literature. In this paper, we investigate the impact of a neurofeedback based BCI game on the enhancement of attention and cognitive skills of healthy subjects. The BCI game is controlled by player's attention-related EEG signal. In the proposed training paradigm, subjects play the neurofeedback game regularly for a period of 5 days. The experimental analysis of player's attention level (measured by entropy values of EEG) and the comparison of cognitive test results demonstrate the benefits of practicing BCI based neurofeedback game in the enhancement of attention/cognitive skills.