The Spider was launched at the 36th Geneva Motor Show in March 1966, and together with the Giulia Sprint GT Veloce tested by the press at an event organised in Gardone Riviera. To choose a name for the spider Alfa Romeo announced a write-in competition, offering an example of the new car as a prize. Over 100 thousand ballots were sent in, the great majority from Italy; the winner was Guidobaldo Trionfi, a man from Brescia, who proposed the name "Duetto" (duet).
However it could not be officially adopted due to trademark issues, and the car was named simply Alfa Romeo Spider 1600.
The Spider's 1,570 cc twin cam engine had dual Weber two-barrel side-draft carburetors, and produced 109 PS DIN (80 kW; 108 hp; or 129 PS SAE). Sparsely fitted inside but including five speed manual transmission, disc brakes 15" wheels fitted with Pirelli Cinturato 155HR15 CA67 tyres. The price on launch in Italy was 2,195,000 lire. In the US the car sold for $3,950 (compared to $3,991 for a Lotus Elan and $2,607 for an MGB). In the UK the car's price was close to a Jaguar E-Type.
In January 1968, in Vietri sul Mare (Salerno), Alfa Romeo introduced the press to its 1750 line of cars, which included the new 1750 Berlina saloon, the Giulia Sprint-based 1750 GT Veloce coupé, and the 1600 Spider-based 1750 Spider Veloce, which replaced the original Spider 1600. All were powered by the same engine, a new 1,779 cc, 118 PS DIN (87 kW; 116 hp; or 132 PS SAE) version of the Alfa Romeo twin cam engine.
Top speed rose to 190 km/h (118 mph). The car did not bear any Spider badging, just a "1750" script below the rear Alfa Romeo badge. During the production run, the front repeater lights were moved ahead of the wheel arches.
While in Europe the 1750 was fitted with two twin horizontal carburettors, starting with model year 1969 models for the North American market had SPICA (Società Pompe Iniezione Cassani & Affini, a subsidiary of Alfa Romeo) mechanical fuel injection. According to Alfa Romeo engine output and performance were unchanged from the carburetted version.
Modifications were also made to the suspension, brakes, electrics, 14" wheels and 165HR14 Pirelli Cinturato CA67 tyres, though the car looked effectively the same. Visible differences were limited to the rear-view mirror repositioned to the door, and badging on the tail, which read "Alfa Romeo" and "iniezione" (injection).
A new lower priced spider, the Spider 1300 Junior, was introduced in June 1968 alongside the GTA 1300 Junior competition coupé.
Its 1,290 cc twin cam engine was the same used on the GT 1300 Junior coupé, and produced 89 PS DIN (65 kW; 88 hp; or 103 PS SAE).
Top speed was 170 km/h (106 mph). From a mechanical standpoint the Junior differed from the 1750 only in engine displacement and output, while inside it lacked some features of the pricier model: namely opening quarter lights, centre console, and the three-spoke wood rimmed steering wheel, replaced by a two-spoke plastic rimmed one. From outside the Junior version could be recognised by its black-coloured lower front bumper and absence of plastic headlamp fairings.
Due to the shape of its long, round tail, the Series 1 Spider is sometimes known by the nickname of "Osso di seppia" (Italian for cuttlebone) or "boat tail" to differentiate it from the "Kamm tail" Series 2. In North America the Series 1 is more commonly known as the "dovetail spider".
6,324 1600 Spiders were made and 2,680 1300 Junior.