Mind wandering in reading, often referred to as mindless reading, is a frequent phenomenon of the human mind. Mindless reading often results in negative consequences on the learning process. In addition to lower performance, negative mood has been addressed as ramification of mind wandering (MW). However, this paper studied the vice-versa - the impact of mood on mind wandering during reading. Mind wandering was studied in two valence conditions: positive (PC) and negative conditions (NC) and its electrophysiological assessment was performed using EEG. Mood was induced using positive and negative images/videos, followed by silent reading experiment. Results showed that mindless reading increased in negative condition than in positive condition. The Poisson regression model showed that sad mood reported in positive condition contributed to a 26% increase in mindless reading frequency. The negative binomial regression results showed 5% increases in mind wandering frequency when aroused by negative valanced stimuli in negative condition. Power spectral analysis showed increased activities in the right temporoparietal region in total alpha (8-12 Hz) and upper alpha band (10 - 13 Hz) during negative mind wandering in comparison with positive mind wandering episodes. Literature have reported association of the right hemisphere with negative/aversive mood. This study showed reduced upper alpha power in TP8 during focused reading (FR) in negative condition than in positive condition. Thus, both during mind wandering and focused reading, increased activities were observed in the right hemisphere only in negative condition, indicating the influence of negative mood irrespective of the tasks. MW and FR showed significant activation only in the temporoparietal region, this region is associated with both discourse processing and mind wandering. As both FR and MW share the same resource (TP8), it indicates that MW during reading could be detrimental to reading performance. This study demonstrated mood to a predictor of mind wandering. This is also an exploratory research which reported the variations in brain activations during mind wandering induced by two valence conditions.