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Improving the production rate of high-value nutraceutical compounds, such as astaxanthin and polyunsaturated fatty acids (PUFAs), is important for the commercialization of <i>Haematococcus pluvialis</i> biorefineries. Here, the effects of a phytohormone, strigolactone analog <i>rac</i>-GR24, on cell growth and astaxanthin and fatty acid biosynthesis in <i>H. pluvialis</i> were investigated. Four concentrations (2, 4, 6, and 8 µM) of <i>rac</i>-GR24 were initially added during 30 days of photoautotrophic cultivation. The addition of <i>rac</i>-GR24 improved cell number density and chlorophyll concentration in <i>H. pluvialis</i> cultures compared to the control; the optimal concentration was 8 µM. Despite a slightly reduced astaxanthin content of 30-d-old cyst cells, the astaxanthin production (26.1 ± 1.7 mg/L) improved by 21% compared to the <i>rac</i>-GR24-free control (21.6 ± 1.5 mg/L), owing to improved biomass production. Notably, at the highest dosage of 8 µM <i>rac</i>-GR24, the total fatty acid content of the treated <i>H. pluvialis</i> cells (899.8 pg/cell) was higher than that of the untreated cells (762.5 pg/cell), resulting in a significant increase in the total fatty acid production (361.6 ± 48.0 mg/L; 61% improvement over the control). The ratio of PUFAs, such as linoleic (C18:2) and linolenic (C18:3) acids, among total fatty acids was high (41.5–44.6% <i>w</i>/<i>w</i>) regardless of the <i>rac</i>-GR24 dose.