Current deﬁnitions of horse personality traits are rather vague, lacking clear, universally accepted guidelines for evaluation in performance tests. Therefore, the aim of the present study was to screen behavioural and physiological measurements taken during riding for potential links with scores the same horses received in the ofﬁcial stallion performance test for rideability and personality traits. Behaviour, heart rate (HR) and HR variability from thirty-six stallions participating in a performance test were recorded repeatedly during their performance test training. Using the coefﬁcient of determination, regression analysis revealed that about 1/3 of variation (ranging between r = 0.26 (“constitution” (i.e. ﬁtness, health)) and r = 0.46 (rideability)) in the personality trait scores could be explained by selecting the three most inﬂuential behaviour patterns per trait. These behaviour patterns included stumbling (with all traits except character), head-tossing (temperament, ride- ability), tail-swishing (willingness to work), involuntary change in gait (character) and the rider’s use of her/his hands (constitution, rideability), voice (temperament) or whip (con- stitution). Subsequent mixed model analysis revealed a signiﬁcant (P < 0.05) inﬂuence of the behaviour pattern “horse-induced change in gait” on character (−0.98 ± 0.31 scores per additional occurrence of change in gaits), of head-tossing (−0.25 ± 0.08 scores) and rider’s use of voice (−0.51 ± 0.25; P = 0.0594) on temperament, and of stumbling on each of the following: willingness to work (−2.5 ± 1.2), constitution (−2.5 ± 1.2 scores; P = 0.0516) and rideability scores (−3.3 ± 1.4). In addition, constitution scores tended (P = 0.0889) to increase with higher low frequency/high frequency heart rate variation ratios (LF/HF), indi- cating a shift towards sympathetic dominance and thus a higher stress load in horses with higher scores for constitution. Rideability scores from the training phase were also sig- niﬁcantly inﬂuenced by head-tossing (−0.5 ± 0.1), and in addition rideability scores from the ﬁnal test were inﬂuenced by the training rider, ranging between average estimated rideability scores of 6.8 ± 0.4 for one training rider and 8.36 ± 0.3 scores for another train- ing rider. Horses ridden with their nose-line predominantly behind the vertical received higher scores for rideability (8.3 ± 0.3) than horses ridden with their nose-line at the vertical (7.7 ± 0.2). These ﬁndings indicate that either judges perceive horses to have a better ride- ability when they readily offer a more extreme poll ﬂexion, or that riders make use of horses’ better rideability by imposing a more extreme poll ﬂexion. Several of the above described associations, but also of the non-existing links (e.g. no association between shying or heart rate and temperament) between behaviour patterns and scores for personality traits are rather surprising, warranting further investigation regarding the underlying causes of these relationships. Some of these behaviour patterns should be considered when redesigning the current guidelines for evaluation of personality traits during breeding horse performance tests, ultimately leading to improved genetic selection for equine personality traits. However, ethical implication of defining aversive behaviour such as head-tossing as an indicator of, for example, poor temperament should not be neglected when devising new guidelines: such aversive behaviour may in fact be an indication of inadequate training techniques rather than poor horse personality.