Antibodies are a promising tool for the fast and selective trace detection of explosives. Unfortunately, the production of high‐quality antibodies is not trivial and often expensive. Therefore, excellent antibodies are a rare and limiting resource in fields such as biosensing, environmental analysis, diagnostics, cancer therapy, and proteomics. Here, we report the synthesis, bioconjugation, and application of the structurally optimized hapten 6‐(2,4,6‐trinitro)‐phenylhexanoic acid to improve the selectivity and sensitivity of antibodies for the detection of one of the most important explosives, trinitrotoluene. With a conjugate of bovine serum albumin and a highly purified N‐hydroxy‐succinimide (NHS)–activated hapten, two rabbits were immunized to obtain polyclonal antibodies. The immunization process was monitored by enzyme‐linked immunosorbent assay to gain information about the progress of antibody titer and affinity. Finally, the polyclonal antibodies reached an affinity constant of (5.1 ± 0.6) × 109 l/mol (rabbit R1) and (2.3 ± 0.2) × 109 l/mol (rabbit R2). The respective assays show a minimum test midpoint (IC50 value) of 0.1 ± 0.01 µg/l (R1) and 0.2 ± 0.02 µg/l (R2) and a working range of 0.005 to 150 µg/l (R1) and 0.007 to 200 µg/l (R2), which corresponds to more than four orders of magnitude for both. This is quite remarkable for a competitive immunoassay, which is often believed to have a narrow dynamic range. The limit of detection was calculated to 0.6 ng/l (R1) and 1.5 ng/l (R2), which is up to 100 times improvement in relation to the assay of Zeck et al. (1999) on the basis of a monoclonal antibody. The excellent selectivity of the polyclonal antibodies was comprehensively examined by determining the cross‐reactivity to common explosives and other nitroaromatics including nitro musk components. The widely held belief that polyclonal antibodies generally display higher cross‐reactivities than monoclonals could be disproved. Copyright © 2012 John Wiley & Sons, Ltd.