  We present the low-resolution spectroscopic and UBVRI broad-band photometric
investigations of the Type IIb supernova 2011fu, discovered in UGC 01626. The
photometric follow-up of this event has been initiated a few days after the
explosion and covers a period of about 175 days. The early-phase light curve
shows a rise followed by steep decay in all bands and shares properties very
similar to that seen in case of SN 1993J, with a possible detection of the
adiabatic cooling phase. Modelling of the quasi-bolometric light curve suggests
that the progenitor had an extended ($\sim 1 \times 10^{13}$ cm), low-mass
($\sim 0.1$ $M_\odot$) H-rich envelope on top of a dense, compact ($\sim 2
\times 10^{11}$ cm), more massive ($\sim$ 1.1 $M_\odot$) He-rich core. The
nickel mass synthesized during the explosion was found to be $\sim$ 0.21
$M_\odot$, slightly larger than seen in case of other Type IIb SNe. The
spectral modelling performed with SYNOW suggests that the early-phase line
velocities for H and Fe\,{\sc ii} features were $\sim 16000$ km s$^{-1}$ and
$\sim 14000$ km s$^{-1}$, respectively. Then the velocities declined up to day
+40 and became nearly constant at later epochs.
