In systems with compressible volumes, long-term pressure oscillations during boiling occur. Flow boiling of distilled water in 11 parallel microchannels covered by a thin, elastic glass has been investigated. The synchronous patterns in such oscillations were investigated by multichannel correlation analysis based on image analysis. The analysis of pixel brightness correlations was performed in parts of the microchannels where an estimated boiling front position was determined using the image analysis method published in the paper (Rafałko et al., 2020). The correlation coefficient calculated between microchannels carried information about phase maldistribution or phase synchronization in the analyzed parts of the exchanger. It has been found that the correlations between two-phase flow in channels have a wave-like form. This wave-like form is related to correlation coefficient maxima located in middle channels—boiling flow was distributed mainly in the middle channels of the exchanger. We found that in the phase of less intense boiling, the correlations between two-phase flow in channels decrease, which causes an increase in the flow maldistribution. The phenomenon of correlations between two-phase flow in distant channels is observed.