In a survey of nearly 2,200 evangelical leaders from 166 countries, 71% identified the influence of secularism as a "major threat" to evangelical Christianity.
This was followed by consumerism (67%), and sex and violence in pop culture (59%).
Only 47% of evangelicals identified the influence of Islam as a major threat.
The survey, by the Pew Research Center's Forum on Religion and Public Life, also found that evangelicals in the Global South are more optimistic about the future of evangelicalism than their brothers and sisters in the Global North.
While seven in ten evangelical Protestant leaders (71%) living in the Global South expected the state of evangelicalism in their countries to be better in five years than it is today, in the Global North evangelical Protestant leaders expected the situation to either be the same (21%) or get worse (33%).
Global South leaders also tended to be more positive about their influence, with 58% saying that the influence of evangelical Christians on life in their countries was increasing.
In the Global North, however, 66% of leaders said evangelicals were losing influence.
Evangelical leaders in the US were the most pessimistic about the prospects for evangelical Christianity in their society, with 82% saying they were losing influence in the US today.
The findings are based on the responses of evangelical leaders who attended the Third Lausanne Congress on World Evangelisation in Cape Town last October.
The survey also questioned the leaders on their beliefs and found near unanimous agreement on areas like the uniqueness of Christ and issues like abortion.
Ninety-six per cent agreed that Christianity is the one, true faith leading to eternal life, while 98% agreed that the Bible is the Word of God.
Ninety-six per cent agreed that abortion is usually or always wrong, while 84% agreed that society should discourage homosexuality.
They were almost evenly split when it came to literal interpretations of the Bible, morality, and drinking alcohol.
Exactly half of the evangelical leaders surveyed believed the Bible should be read literally, word for word. Forty-nine per cent believed it was not necessary to believe in God to be a moral person.
Just over half (52%) said that drinking alcohol was not compatible with being a good evangelical, compared to 42% who felt that it was.