The extremely weak 2-0 O(14) electric quadrupole transition of N-2 has been detected by very high sensitivity Cavity Ring Down spectroscopy near 4518 cm (1). It is the first N2 absorption line in the first over-tone band reported so far from laboratory experiments. By combining a feedback narrowed Distributed Feedback laser diode with a passive cell tracking technique, a limit of detection of alpha(min) similar to 1.2 x 10 (11) cm (1) was achieved after one day of spectra averaging. The N-2 2-0 O(14) line position and line intensity (about 1.5 x 10 (30) cm/molecule) agree with calculated values provided in the HITRAN2012 database. (C) 2016 Elsevier B. V. All rights reserved.