Atmospheric tides and associated dynamics during two major boreal sudden stratospheric warmings (SSWs) have been investigated. The evolutionary Lomb Scargle and wavelet spectral analysis of specular meteor radar (SMR)‐derived hourly winds reveal evidence of non‐linear interactions between the semidiurnal solar tide and the quasi‐20‐day wave (Q20dw) during SSWs. The zonal wavenumber (ZWN) diagnosis indicates possible non‐linear interaction between the dominant semidiurnal migrating tide (SW2) and zonally symmetric 20‐day wave (20dw0) component, producing the secondary waves. The non‐linear interaction between the ZWN 2 component of stationary planetary wave (SPW2) and westward propagating 20‐day wave (20dwW2) in the stratosphere seems crucial to produce the 20dw0. As observed in the SMR‐derived wind spectra, the excited 20dw0 possibly interacts non‐linearly with SW2 to generate secondary waves. Therefore, the present study provides the first observational evidence of a two‐step non‐linear interaction associated with zonally symmetric planetary waves during major SSWs. Plain Language Summary The sun‐synchronous semidiurnal tide (SW2) is a major wave in the middle and high latitude mesosphere and lower thermosphere (MLT). Sudden stratospheric warming (SSW) is a polar winter hemispheric event characterized by enhanced planetary wave (PW) activity. Non‐linear interaction between the two waves produces secondary waves whose frequencies are sum and difference of the primary waves. Further, the secondary waves, having a frequency closely spaced to the tidal frequency, beat with the tide, resulting in modulation of the tidal amplitude by the PW's period due to the non‐linear interaction. The spectral analysis of specular meteor radar‐derived hourly winds supports this notion, and hence provides evidence for non‐linear interactions in the MLT. The dominant PW involved in the interaction is found to be zonally symmetric. The non‐linear interaction between the stationary PW and propagating PW in the stratosphere plays an important role in forcing the zonally symmetric component, that can reach MLT altitudes. Furthermore, non‐linear interaction between SW2 and the zonally symmetric PW produces the observed secondary waves in the MLT in the form of side bands in radar spectra. Overall, the present study provides the first observational evidence of a two‐step non‐linear interaction during SSWs. Key Points Spectral analysis on meteor radar winds provides evidence of non‐linear interaction between semidiurnal tide and quasi‐20‐day wave Possible role of zonal wavenumber 2 stationary planetary wave in forcing zonally symmetric 20‐day wave in the stratosphere First observational evidence of two‐step non‐linear interaction associated with zonally symmetric planetary waves during major sudden stratospheric warmings