Aflatoxins and zearalenone (ZEN) are highly common mycotoxins in maize and maize-based products. This study aimed to report a time-resolved fluorescence immunochromatographic assay (TRFICA) developed using two idiotypic nanobodies for rapid, quantitative, and simultaneous detection of aflatoxin B (AFB) and ZEN in maize and its products. A novel Eu/Tb(III) nanosphere with enhanced fluorescence was prepared as a label and conjugated to anti-idiotypic nanobody (AIdnb) and monoclonal antibody (mAb). On the basis of nanosphere-antibody conjugation, two patterns of competitive time-resolved strip methods (AIdnb-TRFICA and mAb-TRFICA) were established and compared. The half inhibition concentration of AIdnb-TRFICA was 0.46 and 0.86 ng·mL for AFB and ZEN, which was 18.3- and 20.3-fold more sensitive than that of mAb-TRFICA for AFB and ZEN, respectively. Under optimal conditions, AIdnb-TRFICA for dual mycotoxin was established and provided a quantitative relationship ranging from 0.13 to 4.54 ng·mL for AFB and 0.20 to 2.77 ng·mL for ZEN, with a detection limit of 0.05 and 0.07 ng·mL in the buffer solution, respectively. AIdnb-TRFICA showed good recoveries (72.6%-106.6%) in samples and was applied to detect dual mycotoxin in maize samples with satisfying results. To the best of our knowledge, it is the first report about a time-resolved strip method based on AIdnbs for dual mycotoxin.