In northern Australia and nearby Timor-Leste, saltwater crocodile (Crocodylus porosus) populations were seriously depleted historically but recovered rapidly after protection: 1969–1974 in northern Australia, and 2000–2005 in Timor-Leste. In both places, recovery caused increased rates of human-crocodile conflict (HCC). Within northern Australia, the crocodile recovery and HCC have been documented over time. In contrast, this has not been the situation in Timor-Leste, where we investigated HCC based on 130 attack records (1996–2014; 52% fatal). In 1996–2006, 0.55 attacks/year were reported in Timor-Leste. By 2007–2014, 9 years later, a 23-fold increase had occurred (13 attacks/year). Traditional subsistence fishing (82.5% of all attack records) is the highest risk activity, followed by bathing (7.5%) and water collecting (4.2%). Although the human population was correlated with crocodile attacks in Timor-Leste, it likely does not explain the dramatic increase in crocodile attacks. Alternatively, crocodile numbers may have increased, either in the remnant resident crocodile population, or via migrants from elsewhere. Permanent crocodile habitat is limited, and limited breeding does not explain the high number of large crocodiles, and consequent increase in attacks in such a short time. A plausible explanation, consistent with traditional knowledge in Timor-Leste, is that the influx of large crocodiles attacking people are migrants from Australia. We examined this possibility from available sources. Within Australia crocodiles have recovered since protection and they regularly invade adjacent habitats, such as Darwin harbor, where they are removed to prevent attacks on people. Saltwater crocodiles have been sighted at oil rigs, in the open ocean, moving between northern Australia and the south coast of Timor-Leste. The likelihood of crocodiles migrating from Australia to Timor-Leste raises obvious conservation, moral, and ethical dilemmas when conserving a large dangerous predator in one country to increase abundance results in dispersal to another country, where the predator attacks and kills people.