At last check Apple shares were rising 2.8% to $128.36, while Tesla rose 4.7% to $463.62.
On Friday Apple shares closed at $499.23 Friday and Tesla at $2,213.40.
Analysts reacted positively when Apple declared the stock split in its third-quarter earnings report.
Apple, which last month became the first company to reach a $2 trillion market capitalization, said on its third quarter earnings call that the split was intended to make its stock more accessible to more investors.
The stock has more than quadrupled in value since Apple's last split in 2014.
Stocks that split have historically outperformed the market following the distribution, as investors see the moves as signaling confidence in the company's longer-term growth prospects.
The Cupertino, Calif., tech giant's stock split will result in changes in the Dow Jones Industrial Average.
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"The index changes were prompted by DJIA constituent Apple Inc.'s decision to split its stock 4 for 1, which will reduce the index's weight in the Global Industry Classification Standard Information Technology sector," S&P Dow Jones Indices said in a statement.
Tesla shares have gained more than 50% since the Palo Alto, Calif., electric-vehicle company on Aug. 11 unveiled plans for the split. The electric vehicle maker is moving toward a likely inclusion in the S&P 500 stock index this fall.
Credit Suisse analysts suggest the S&P 500 inclusion could trigger even more activity in Tesla stock, with "significant" incremental buying of around 18 million shares - some 10% of the total outstanding - from passive investors and fund managers that track the benchmark index.