Context :

Aims : We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 ( V = 5.79 ) .
We also attempt to detect a magnetic field in the target .

Methods : We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods .
We determine the fundamental parameters of the star , as well as its abundances from the most prominent spectral lines .
We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field , assuming a dipole field .

Results : In the CoRoT data , we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its ( sub- ) multiples .
Given the shape of the phase-folded light curve and the absence of binary motion , we interpret the dominant variability in terms of rotational modulation , with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations .
Our results are consistent with the absence of variability in the Hipparcos light curve .
The spectroscopy leads to a projected rotational velocity of 72 \pm 2 km s ^ { -1 } and does not reveal periodic variability or the need to invoke macroturbulent line broadening .
No signature of a magnetic field is detected in our data .
A field stronger than \sim 500 G at the poles can be excluded , unless the possible non-detected field were more complex than dipolar .

Conclusions : The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars .