We present the results of a 9.3-deg2 infrared (ZYJHK) survey in the Upper Scorpius association extracted from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey Early Data Release. We have selected a total of 112 candidates from the (Z - J,Z) colour-magnitude diagram over the Z = 12.5-20.5 magnitude range, corresponding to M = 0.25-0.01 Msolar at an age of 5 Myr and a distance of 145 pc. Additional photometry in J and K filters revealed most of them as reddened stars, leaving 32 possible members. Among them, 15 have proper motion consistent with higher-mass members from Hipparcos and optical spectra with strong Hα in emission and weak gravity features. We have also extracted two lower-mass candidate members for which no optical spectra are in hand. Three members exhibit strong Hα equivalent widths (>20 Å), suggesting that they could still undergo accretion, whereas two other dwarfs show signs of chromospheric activity. The likelihood of the binarity of a couple of new stellar and substellar members is discussed as well. Based on observations made with the United Kingdom Infrared Telescope, operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council. Based on observations collected with the European Southern Observatory (ESO) 3.6-m/EFOSC2 at ESO, La Silla, Chile (ESO programme 076C-0237). ‡ E-mail: nl41 [at] star.le.ac.uk (nl41[at]star[dot]le[dot]ac[dot]uk)