Although reliable statistics are not available, it is estimated that half of the population of Eritrea is Christian, including Orthodox, Catholic, and other sub groups and the other half is Sunni Muslim. Approximately 2 percent of the population practice traditional indigenous religions. Approximately 3 percent of the population is Roman Catholic, while groups that constitute less than 0.1 percent of the population include Protestants, Seventh-day Adventists, Jehovah's Witnesses, and Bahá'ís.
Although reliable statistics are not available 42 percent of the population are followers of Christianity and other religions and the rest are followers of the Muslim religion. Approximately 4 percent of the population is Roman Catholic, while groups that constitute less than 0.1 percent of the population include Protestants, Seventh-day Adventists, Jehovah's Witnesses, Buddhist, Hindus, and Baha'is. Approximately less than 0.1 percent of the population practice traditional indigenous religions. The population in the eastern and western lowlands is predominantly Muslim and predominantly Christian in the highlands. There are very few atheists. Religious participation is high among all ethnic groups.
All Eritrean Muslims practice Sunni Islam. Generally, the eastern and western lowlands are predominantly Muslim while the highlands are predominantly Christian.
During the past century, Islam flourished in Eritrea under Italian rule ( 1882 – 1941 ) but was repressed under Ethiopian rule ( 1951 – 91 ). 
One 2007 estimate is that Christianity is the religion of about 50 percent of the population of Eritrea. Around 44 percent of citizens belong to the Eritrean Orthodox Tewahdo Church, which used to belong to the formerly Coptic Ethiopian Orthodox Tewahedo Church. In 1998 the Archbishop of Asmara was elevated to the rank of patriarch.
The Eritrean Catholic Church has dioceses of Asmara, Keren and Barentu. There are approximately 150,000 Catholics in Eritrea, who follow both the Latin rite and the Eritrean rite. There are three territorial jurisdictions in the country known as eparchies.
Protestants in Eritrea number about 91,232, making up 2% of the population. A minor church is the Kale Hiywot Church of Eritrea. Protestant denominations include Christian Brethren, Evangelical Church Mekane Yesus, Evangelical Church of Eritrea, Lutheran Church of Eritrea, Middle East General Mission, and Seventh-day Adventist Church.
The religious freedom of Christians not belonging to registered groups (the Eritrean Orthodox Church, the Evangelical (Lutheran) Church of Eritrea, Islam, Seventh-day Adventist Church and the Roman Catholic Church) is severely restricted (see Freedom of religion, below).
Groups that constitute less than 1 percent of the population includes Bahá'ís. Approximately less than 2 percent of the population practice traditional indigenous religions. The last native Jew in Eritrea, Sami Cohen, attends to the Asmara Synagogue and cemetery..
The population in the eastern and western lowlands is predominantly Muslim and predominantly Christian in the highlands. There are very few atheists. Religious participation is high among all ethnic groups.
Within geographic and ethnic groups, the majority of the Tigrinya are Orthodox Christian, with the exception of the Djiberti Tigrinya, who are Muslim. Most members of the Tigre, Saho, Nara, Afar, Rashaida, Beja, and Bilen ethnic groups are Muslim. Approximately 40 percent of the Blen are Christian, the majority being Catholic. More than half of the Kunama are Catholic, with a large minority of Muslims and some who practice traditional indigenous religions. The central and southern highlands, which are generally more developed than the lowlands, are populated predominantly by Christian Tigrinyas as well as some Muslim Djiberti Tigrinya and Saho. The Afar and Rashaida, as well as some Saho and Tigre, live in the eastern lowlands. The Blen live on the border between the western lowlands and the central highlands and are concentrated in the Keren area, which also includes a significant minority of Tigre and Tigrinya speakers. The Beja, Kunama, Nara, and most Tigre live in the western lowlands.
The Government severely restricts freedom of religion for groups that it has not registered and infringes upon the independence of some registered groups. The 1997 Constitution provides for religious freedom; however, the Constitution has not been implemented. Following a 2002 government decree that religious groups must register, the Government closed all religious facilities not belonging to the country's four principal religious groups—the Eritrean Orthodox Church, the Evangelical (Lutheran) Church of Eritrea, Islam, and the Roman Catholic Church. The Government harasses, arrests, and detains members of independent evangelical groups, Pentecostals, Jehovah's Witnesses, and a reform movement within the Eritrean Orthodox Church and seeks greater control over the four approved religious groups. The Government failed to register any of the four religious groups who applied in 2002 for registration, and it restricted religious meetings and arrested individuals during religious ceremonies, gatherings, and prayer meetings. There were also reports of forced recantations. There have also been reports of torture of religious detainees, and some religious detainees have been held in harsh conditions that included extreme temperature fluctuations with limited or no access to family.
Foreign missionaries operate with some restrictions. Some missionaries and representatives of the restricted unregistered religious groups are present but keep an extremely low profile for fear of abuse of their congregations.
Citizens generally are tolerant of one another in the practice of their religion, with the exception of societal attitudes toward Jehovah's Witnesses and Pentecostal groups. The Government requires citizens to perform national service in the military or face incarceration, but it has no programs for alternative national service that would permit Jehovah's Witnesses and others whose faith precludes military service to satisfy the requirement. Some individuals who viewed failure to perform military service as a sign of disloyalty encouraged harassment of these religious groups and reported their activities to the Government.