Chiang Kai-shek was born in Xikou, a town that is approximately 30 kilometers southwest of downtown Ningbo, in Fenghua County, Ningbo Prefecture, Zhejiang Province. However, his ancestral home, a concept important in Chinese society, was the town of Heqiao in Yixing County, Wuxi, Jiangsu (approximately 38 km (24 mi) southwest of downtown Wuxi, and 10 km (6.2 mi) from the shores of the Lake Tai).

His father, Chiang Zhaocong, and mother, Wang Caiyu, were members of an upper to upper-middle-class family of salt merchants. His father died when Kai-shek was only eight years of age, and he wrote of his mother as the "embodiment of Confucian virtues." In an arranged marriage, Chiang was married to a fellow villager by the name of Mao Fumei. Chiang and Mao had a son, Ching-Kuo and a daughter Chien-hua.

Chiang grew up in an era in which military defeats and civil wars among warlords had left China destabilized and in debt, and he decided to pursue a military career. He began his military education at the Baoding Military Academy, in 1906. He left for a preparatory school for Chinese students to enter Rikugun Shikan Gakko in Japan in 1907. There he was influenced by his compatriots to support the revolutionary movement to overthrow the Qing Dynasty and to set up a Chinese republic. He befriended fellow Zhejiang native Chen Qimei, and, in 1908, Chen brought Chiang into the Tongmenghui, a precursor organization of the Kuomintang. Chiang served in the Imperial Japanese Army from 1909 to 1911.

Chiang returned to China in 1911 after learning of the outbreak of the Wuchang Uprising, intending to fight as an artillery officer. He served in the revolutionary forces, leading a regiment in Shanghai under his friend and mentor Chen Qimei, one of Sun's chief lieutenants. The revolution which aimed at the overthrow of the Qing Dynasty ultimately succeeded. Chiang became a founding member of the Kuomintang.

After the takeover of the Republican government by Yuan Shikai and the failed Second Revolution, Chiang, like his Kuomintang comrades, divided his time between exile in Japan and havens in Shanghai's foreign concession areas. In Shanghai, Chiang also cultivated ties with the underworld gangs dominated by the notorious Green Gang and its leader Du Yuesheng. On February 15, 1912, several KMT members which included Chiang, killed Tao Chengzhang, the leader of the Restoration Society, in a Shanghai French Concession hospital, thus ridding Sun Yat-sen of his chief rival. (There is no known evidence that Sun Yat-sen himself was involved in the affair in any way.)

On May 18, 1916 agents of Yuan Shikai assassinated Chen Qimei. Chiang succeeded Chen as leader of the Chinese Revolutionary Party in Shanghai. Sun Yat-sen's career was at the lowest point then, with most of his old Revolutionary Alliance comrades refusing to join him in the exiled Chinese Revolutionary Party.

In 1917, Sun Yat-sen moved his base of operations to Guangzhou and Chiang joined him in 1918. Sun, at the time was largely sidelined and, without arms or money, was soon expelled from Guangzhou in 1918 and exiled again to Shanghai, but was restored again with mercenary help in 1920. However, a rift had developed between Sun, who sought to militarily unify China under the KMT, and Guangdong Governor Chen Jiongming, who wanted to implement a federalist system with Guangdong as a model province. On June 16, 1923 Chen attempted to assassinate Sun from Guangzhou and had his residence shelled. Sun and his wife Soong Ching-ling narrowly escaped under heavy machine gun fire and were rescued by gunboats under Chiang's direction. The incident earned Chiang Sun Yat-sen's trust.

Sun regained control in Guangzhou in early 1924 with the help of mercenaries from Yunnan, and accepted aid from the Comintern. He then undertook a reform of the Kuomintang and established a revolutionary government aimed at unifying China under the KMT. That same year, Sun sent Chiang Kai-shek to spend three months in Moscow studying the Soviet political and military system. During his trip in Russia, Chiang met Trotsky and other Soviet leaders, but Chiang quickly drew the conclusion that the Bolshevik's way did not suit China. Chiang Kai-shek returned to Guangzhou and in 1924 was appointed Commandant of the Whampoa Military Academy by Sun. Chiang, who had once resigned from the office for one month in disagreement with Sun's too close cooperation with the Comintern, returned later at Sun's demand. The early years at Whampoa allowed Chiang to cultivate a cadre of young officers loyal to KMT and himself. However, the academy was rife with communists, many of whom later became leaders of the Chinese Red Army including Zhou Enlai, who was selected to be Whampoa's deputy Political Commissar. Chiang was deeply critical of the Kuomintang-Communist Party United Front, foreseeing the Communists' plan to take over the KMT from within. By 1925, Chiang's proto-army was scoring victories against local rivals in Guangdong province.

Throughout his rise to power, Chiang Kai-shek also benefited from membership of the nationalist Tiandihui fraternity, to which Sun Yat-Sen also belonged, and which remained a source of support during his leadership of China and later Taiwan.

Sun regained control in Guangzhou in early 1924 with the help of mercenaries from Yunnan, and accepted aid from the Comintern. He then undertook a reform of the Kuomintang and established a revolutionary government aimed at unifying China under the KMT. That same year, Sun sent Chiang Kai-shek to spend three months in Moscow studying the Soviet political and military system. During his trip in Russia, Chiang met Trotsky and other Soviet leaders, but Chiang quickly drew the conclusion that the Bolshevik's way did not suit China. Chiang Kai-shek returned to Guangzhou and in 1924 was appointed Commandant of the Whampoa Military Academy by Sun. Chiang, who had once resigned from the office for one month in disagreement with Sun's too close cooperation with the Comintern, returned later at Sun's demand. The early years at Whampoa allowed Chiang to cultivate a cadre of young officers loyal to KMT and himself. However, the academy was rife with communists, many of whom later became leaders of the Chinese Red Army including Zhou Enlai, who was selected to be Whampoa's deputy Political Commissar. Chiang was deeply critical of the Kuomintang-Communist Party United Front, foreseeing the Communists' plan to take over the KMT from within. By 1925, Chiang's proto-army was scoring victories against local rivals in Guangdong province.

Throughout his rise to power, Chiang Kai-shek also benefited from membership of the nationalist Tiandihui fraternity, to which Sun Yat-Sen also belonged, and which remained a source of support during his leadership of China and later Taiwan.