  We have studied bulk viscosity in the modified $f(Q, T)$ gravity theory
formalism, where $Q$ represents the non-metricity and $T$ denotes the trace of
energy-momentum tensor within a flat Friedmann-Lema\^{i}tre-Robertson-Walker
metric (FLRW). Here, we have explicitly considered the effective equation of
state, which includes a bulk viscosity term, and obtained the exact solutions
by assuming a specific form of $f(Q, T)=\alpha Q+\beta T$, where $\alpha$ and
$\beta$ are constants. Furthermore, we have found constraints on the model
parameters with some external datasets, such as the revised Hubble datasets
consisting of 57 data points, Baryon acoustic oscillations (BAO) datasets, and
the newly published Pantheon samples with 1048 points to obtain the best
fitting values of the model parameters. The obtained model is found to be in
good agreement with observations. In addition, we have analyzed the
cosmological behavior of the density parameter, the equation of state (EoS)
parameter ($\omega$), and the deceleration parameter ($q$). The results are
satisfying to the standard scenario of recent findings of cosmology. The
universe appears to be evolving from a decelerated to an accelerated phase. The
EoS parameter is further in the quintessence phase, indicating that the
universe is accelerating. Finally, we can deduce that the accumulation of bulk
viscosity as effective dark energy supports the current accelerated expansion
of the universe.
