Building on recent NMR experiments [A. Orlova et al., Phys. Rev. Lett. 118, 067203 (2017)], we theoretically investigate the high magnetic field regime of the disordered quasi-one-dimensional S = 1 antiferromagnetic material Ni(Cl1−xBrx)2-4SC(NH2)2. The interplay between disorder, chemically controlled by Br-doping, interactions, and the external magnetic field, leads to a very rich phase diagram. Beyond the well-known antiferromagnetically ordered regime, analog of a Bose condensate of magnons, which disappears when H ≥ 12.3 T, we unveil a resurgence of phase coherence at higher field H ∼ 13.6 T, induced by the doping. Interchain couplings stabilize finite temperature long-range order whose extension in the field -temperature space is governed by the concentration of impurities x. Such a "mini-condensation" contrasts with previously reported Bose-glass physics in the same regime, and should be accessible to experiments.Introduction.-Interacting quantum systems in the presence of disorder have been intensively studied for several decades, leading to fascinating physics, e.g. the Kondo effect [1], the many-body localization transition [2], or the superfluid to Bose-glass (BG) [3,4] transition at finite disorder for lattice bosons [5][6][7]. While counterintuitive, in some situations disorder may enhance long-range order, as discussed for inhomogeneous superconductors [8][9][10]. Perhaps even more surprisingly, doping gapped antiferromagnets with a finite concentration of magnetic or non-magnetic impurities can fill up the bare spin gap with localized levels [11-13] which may eventually order, in the strict sense of macroscopic long-range order (LRO) at low temperature. Such an impurity-induced ordering mechanism of the type "order from disorder" [14,15] [21]. Nevertheless, only a few studies have focused on the effect of an external field [22][23][24][25][26][27].In this Letter, building on recent nuclear magnetic resonance (NMR) experiments [28], we achieve a realistic theoretical study of the high magnetic field regime of Ni(Cl 1−x Br x ) 2 -4SC(NH 2 ) 2 (DTNX): a threedimensional antiferromagnetic (AF) system made of weakly coupled chains of S = 1 spins subject to singleion anisotropy [panels (b-c) of Fig. 1]. Note that the S = 1 chains are not of Haldane type, due to the large anisotropy D [29]. In the absence of chemical disorder (x = 0), NiCl 2 -4SC(NH 2 ) 2 (DTN) provides a very good realization of magnetic field-induced Bose-Einstein condensation (BEC) in a quantum spin system [30][31][32][33] between two critical field H clean