Dickey was elected as a Republican to the Fortieth Congress to fill the vacancy caused by the death of Thaddeus Stevens and on the same day was elected to the Forty-first Congress. He was reelected to the Forty-second Congress. He was not a candidate for renomination in 1872. He was a delegate to the State constitutional convention at Harrisburg, Pennsylvania in 1873. He resumed the practice of law in Lancaster and died in 1876. He was interred in Woodward Hill Cemetery.