Previous studies have reported inconsistent results when attempting to use pre-partum supplementation to improve re-conception rates in first-lactation heifers in northern Australia. It has been speculated that where no improvement in re-conception rates was found that it may have been because supplementation was stopped before the wet season began, and the benefits from supplementation were lost when heifers lost weight between the end of supplementation and the start of the wet season. This study was conducted to determine whether re-conception rates in Brahman first-lactation heifers in the Victoria River District (VRD) could be reliably improved by pre-partum supplementation with high protein supplements (at a rate of 0.4% of liveweight per day). Re-conception rates were significantly higher in supplemented (SUP) heifers in each of the 3 years of this study (re-conception rates were an average of 42 % units higher in SUP heifers over the 3 years). It was concluded that feeding pre-partum protein supplements for a period of at least 100 days until green grass is available at the start of the wet season is a reliable method of increasing re-conception rates in first-lactation heifers in the VRD. However, even with large increases in re-conception rate, the profitability of supplementation strategies in northern Australia need to be carefully evaluated due to high on-farm costs of supplements. Profitability is also adversely affected when the feeding period is extended due to a late start to the wet season.