This study is a critical analysis of the Pakistan-Afghanistan relations. A variety of problems are hindering the cordial relations of the two states. The commonalities are many but the differences are strong and rapprochement seems difficult. The study depicts that both the states are apprehensive of each other. Mainly the non acceptance of international border i.e. Durand Line, irredentist territorial claims and Pashtunistan issues by Afghanistan and the perceived so called policy of strategic depth by Pakistan are the impediment. In the last forty years Afghanistan has faced civil war and foreign intervention. Since then Pakistan finds itself at the forefront of the efforts to bring peace and stability in Afghanistan, as a "frontline state". In 1970s and 1980s it opposed the U.S.S.R. invasion and since 2001 it has supported the U.S. invasion, ditching the Taliban regime. The presence of foreign forces in Afghanistan has affected Pakistan's sovereignty due to drone and border attacks. Pakistan wants to safeguard its legitimate interests i.e. peaceful, stable and friendly Afghanistan. At the same time it wants that Afghanistan may not be used by any regional country against the interests of Pakistan. In Afghanistan different ethnicities are apprehensive of each other and combine together against the Pashtuns dominance of the past. All the other ethnicities strived hard to find a place in the Afghan state and are adamant to preserve their restored identities. The study focuses on the effects of U.S. drawdown of forces, signing of Bilateral Security Agreement and Status Of Forces Agreement on Pakistan-Afghanistan relations. It has given new impetus to peace efforts. However, the Taliban insurgency has been deadliest in 2014 with peace nowhere. The efforts of U.S. and the regional states to ensure peace have been evaluated. The study explains the phenomenon of mistrust and hostile relations of the two states in realist perspective. Geostrategic and geo-economics reasons make it necessary for both states to have cordial relations. A peaceful settlement is interest of people of Pakistan and Afghanistan and the region, the alternative is a scary civil war.