<p>Females of many species that exhibit exclusive paternal care prefer parental over non-parental males. According to the essential male care model, once males fulfill the minimum care requirements for offspring survival, they should allocate their surplus energy to advertise their good body condition and increase their attractiveness. To test this prediction, we conducted a field experiment using the harvestman <i>Iporangaia pustulosa</i>, in which males provide exclusive parental care. Employing a full factorial design, we manipulated the body condition of parental males (well-fed and poorly fed) and the status of their sexually dimorphic glands (blocked and unblocked), which likely release sexual pheromones. Then, we recorded males’ probability of receiving new eggs and estimated their mean fitness. Parental males in good condition with unblocked glands had a higher probability of receiving new eggs compared to those in poor condition with blocked glands. Males in the other two experimental groups exhibited intermediate values. Parental males with unblocked glands had a mean fitness 1.38 times higher when in good condition. Additionally, parental males in good condition had a mean fitness 3.48 times higher when the glands were unblocked. These results suggest that the production of sexual pheromones in harvestmen is condition-dependent and emphasize the significance of sexual advertisement as an indicator of male quality. Overall, our findings support the predictive power of the essential male care model and shed light on the interplay between body condition, sexual advertisement, and mating success in species exhibiting exclusive paternal care.</p>