Answered by our Shaykh, the ‘Allaamah, the Sincere Adviser, Abu ‘Abdirrahman Yahya bin ‘Ali Al-Hajoori – may Allaah preserve him –
Does the one praying by himself say ‘Ameen’ after reading suratul faatihah?
Yes he says Ameen due to the hadeeth of Abee musa (may Allah be pleased with him):
“فقولوا آمين يجبكم الله”
So say Ameen and Allah will answer you. [Narrated by muslim]
Translated by : Abu Huthayfah Saamy Al-hindy
Original Fatwa : http://m.sh-yahia.net/show_s_fatawa_46.html